PRAXIS BUSINESS SCHOOL

Work Measurement

A report

submitted to

Prof. AJAY MAJUMDAR

In partial fulfilments of the requirements of the course

Production and Operations Management

On 17-11-2008

By

Mohit Almal

Rupesh Agarwal

What is work measurement?

Work Measurement is a term which covers several different ways of finding out how long a

job or part of a job should take to complete. It can be defined as the systematic

determination, through the use of various techniques, of the amount of effective physical

and mental work in terms of work units in a specified task. The work units usually are given

in standard minutes or standard hours.

Work measurement is the careful analysis of a task, its size, the method used in its

performance, and its efficiency. The objective is to determine the workload in an operation,

the time that is required, and the number of workers needed to perform the work

efficiently. Work measurement helps to determine the time spent performing any process

and offers a consistent, comparable methodology for establishing labor capacities.

Work measurement can be extremely effective at informing supervisors of the working

times and delays inherent in different ways of carrying out work. The purpose of a

measurement method is to achieve full coverage of the work to be measured.

A good work measurement system has many benefits. It helps to reduce labor costs,

increase productivity, and improve supervision, planning, scheduling, performance

appraisal, and decision making.

It can also be defined as

Work Measurement is a term which covers several different ways of finding out how long a

job or part of a job should take to complete. It can be defined as the systematic

determination, through the use of various techniques, of the amount of effective physical

and mental work in terms of work units in a specified task. The work units usually are given

in standard minutes or standard hours.

Why should we need to know how long a job should take? The answer to this question lies

in the importance of time in our everyday life. We need to know how long it should take to

walk to the train station in the morning, one needs to schedule the day's work and even

when to take out the dinner from the oven.

The need to measure work

Work measurement techniques are intended to reveal the work content of a task. In order

that different tasks may be compared, the work content is always measured in the same

units, those of time. The time taken to complete any job is considered to be the time which

a qualified worker- that is, one who has necessary physical and mental attributes and has

acquired the necessary skill- would take if working without over exertion throughout a

normal period while applying him/herself to the job.

Why should we need to know how long a job should take? The answer to this question lies

in the importance of time in our everyday life. We need to know how long it should take to

walk to the train station in the morning, one needs to schedule the day's work and even

when to take out the dinner from the oven.

In the business world these standard times are needed for:

� Planning the work of a workforce,

� Manning jobs, to decide how many workers it would

need to complete certain jobs,

� Scheduling and loading the tasks allocated to people

� Costing and budgeting the work for estimating contract

prices and costing the labour content in general

� Calculating the efficiency or productivity of workers -

and from this:

� Providing fair returns on possible incentive bonus

payment schemes.

� Line balancing and establishing manning levels.

� Efficiency comparison

� Comparison of alternative methods

Selecting the most appropriate methods of work measurement

The method chosen for each individual situation to be measured depends on several factors

which include:

� The length on the job to be measured in time units

� The precision which is appropriate for the type of work in terms of time units (i.e. should it

be in minutes, hundredths or thousandths of a minute)

� The general cycle-time of the work, i.e. does it take seconds, minutes or days to complete

The length of time necessary for the completion of the range of jobs can vary from a few

seconds in highly repetitive factory work to several weeks or months for large projects such

as major shutdown maintenance work on an oil refinery. It is quite clear that using a stop-

watch, for example, on the latter work would take several man-years to time to measure!

Thus, more "overall" large-scale methods of timing must be employed.

The precision is an important factor, too. This can vary from setting times of the order of "to

the nearest thousandth of a minute" (e.g. short cycle factory work) to the other end of the

scale of "to the nearest week" (e.g. for large project work).

These are the dominant factors that affect the choice of method of measurement.

The methods

The most commonly used methods of work measurement are:

(1) Time study

(2) Pre Determined Motion Time System (PMTS)

(3) Estimating

(4) Activity sampling

Time Study

What is it?

Time study is a tried and tested method of work measurement for setting basic times and

hence standard times for carrying out specified work. Its roots are back to the period

between the two World Wars.

The aim of time study is to establish a time for a qualified worker to perform specified work

under stated conditions and at a defined rate of working.

This is achieved by a qualified practitioner observing the work, recording what is done and

then timing (using a time measuring device) and simultaneously rating (assessing) the pace

of working.

The requirements for taking a time study are quite strict.

Conditions:

� the practitioner (observer) must be fully qualified to carry out Time Study

� the person performing the task must be fully trained and experienced in the work

� the work must be clearly defined and the method of doing the work must be effective

� the working conditions must be clearly defined

There are two main essentials for establishing a basic time for specified work i.e. rating and

timing.

Some terminology explained

Timing

The observer records the actual time taken to do the element or operation. This usually is in

centiminutes (0.01 min.) and is recorded, using a stop-watch or computerized study board.

Rating.

When someone is doing work his/her way of working will vary throughout the working period and

will be different from others doing the same work. This is due to differing speeds of movement,

effort, dexterity and consistency. Thus, the time taken for one person to do the work may not be the

same as that for others and may or may not be 'reasonable' anyway. The purpose of rating is to

adjust the actual time to a standardized basic time that is appropriate and at a defined level of

performance. Rating is on a scale with 100 as its standard rating.

Elements

A complete job usually will be too long and variable to time and rate in one go, so it would be

analysed into several smaller parts (elements) which, separately, will each be timed and rated.

Basic time

This is the standardised time for carrying out an element of work at standard rating.

Example: An observer times an element as 30 centiminutes (cm) and because it is

performed more slowly than the standard 100, he rates it as 95. Thus the basic time is 95%

of 30 or 28.5 basic cm. The formula is: (actual time x rating)/100.

Allowances

Extra time is allowed for various conditions which obtain, the main ones being relaxation

allowance for:

� Recovery from the effort of carrying out specified work under specified conditions (fatigue

allowance)

� Attention to personal needs

� Adverse environmental conditions,

plus:

� Others concerned with machine operations

Frequency

The basic time is the time for a complete cycle to be performed but as not all elements are repeated

in every cycle their times per average cycle must be pro rata. In the example which follows, element

2 only occurs once every eight cycles so it’s basic time is one eighth of the element time, per cycle.

Similar treatment for element 7 (one twelfth).

Standard time:

Basic time + allowances

Time study employs stopwatches to determine the standard time for completing a job. The

process starts by analysing the job into its basic elements. This stage permits the critical

appraisal of the method of performing the job and then the improvement of the method

wherever possible.

The next stage is to time each element of the revised procedure so that the time for the

total job is built up.

Finally, a rating adjustment is made to take account of the speed and effectiveness of the

operator, and a relaxation allowance is calculated to provide for the effect of fatigue over a

longer period. The relaxation allowance varies according to the job, but is typically 10 to 15

per cent.

The end result is the time for the task defined in standard minutes, which is the time the

experienced worker of average ability should take to do the task while taking the normal

amount of rest from fatigue and for personal needs. Such a worker should produce at an

average rate of 60 standard minutes per 60 clock minutes over the whole day or shift

without undue strain or fatigue. On the British Standards Institute scale this is called a 100

rating (ie 60/60 × 100) and is referred to as standard performance. A worker who takes 80

clock minutes to do 60 standard minutes' work will be working at a 75 rating, ie 60/80 × 100.

An example of a time study - extracts from the two main documents in time study follow:

Time study observation sheet

Department: Main Stores Section: Goods Inwards Summary

A Study ends: 10.35 am

B Study starts: 10.03 am

C Study time: 32 min.

D Check times: 1.68 min.

E Total study time: 33.68 min.

F Elapsed time: 34 min.

G Difference F-E 0.32 min.

H Timing error: G/F% 0.9%

Section head: E. Thompson

Analyst J.Allen Date: 12 July

Operation: Raise and process Goods Received Note

Element

number Element Description rating

observed time

(cm)

basic time

(cm)

1 Look out relevant Purchase Demand (PD) 90 30 27.0

2 Obtain pad of Goods Received notes (GR) 80 95 76.0

3 Make out GR note 80 45 36.0

4 Pin green copy to PD and place in internal

post bin 90 10 9.0

5 File white copy 75 22 16.5

6 Pin other 3 copies to goods and place goods

on pallet 80 17 13.6

1 Repeat 80 33 26.4

3

75 46 34.5

4

75 10 7.5

(Etc.) (Etc. Etc.)

(Etc. Etc.)

Time study analysis sheet

Department: Main Stores Section: Goods

Inwards

Section head: E. Thompson Date: 12-Jul

Operation: Raise and process

Goods Received Note Analyst J.Allen

El. Element Description basic times (b.min) RA% std.mins.

basic t. frequency b.t. x freq. (sm)

1 Look out relevant

Purchase Demand (PD) 29 01-Jan 0.29 10 0.319

2 Obtain pad of Goods

Received notes (GR) 75 01-Aug 0.094 10 0.103

3 Make out GR note 38 01-Jan 0.38 10 0.418

4 Pin green copy to PD and

place in internal post bin 9 01-Jan 0.09 10 0.099

5 File white copy 15 01-Jan 0.15 10 0.165

6

Pin other 3 copies to

goods and place goods on

pallet

17 01-Jan 0.17 15 0.196

7 Move pallet to stores 96 01-Dec 0.08 18 0.094

Total sm = 1.394

Time Study measures how long it takes an average worker to complete a task at a normal

pace. The actual time taken by the above-avg. operation must be increased, and the time

taken by the below-avg. must be reduced to the value representative of normal

performance. Performance rating is a technique for equitably determining the time required

to perform a task by the normal operator after the observed values of the operation under

study have been recorded. A “normal” operator is defined as a qualified, thoroughly

experienced operator who is

working under conditions as they customarily prevail at the work station, at a pace that is

neither fast nor slow, but representative of average Allowance Factor: Addition of an

allowance to take care of the many interruptions, delays, and slowdowns brought on by

fatigue which enter into every work assignment (e.g. car trip) Frederick W. Taylor -1881, he

started to develop time study, started at a machine shop at home with his family.

Tools: Stopwatch & Clipboard.

Tools Used Today:

Computers

Bar codes

Accustudy Software

Stopwatch Time Study Basic Steps

1. Establish the standard job method

2. Break down the job into elements

3. Study the job

4. Rate the worker’s performance (RF)

5. Compute the average time (t)

6. Compute the normal time - Normal Time = (Elemental average) (rating factor)

Nt = (t) (RF) Normal Cycle Time = NT = Nt

7. Compute the standard time - Standard Time = (normal cycle time)

(1+allowance factor), ST = (NT) (1 + AF)

(2) Standard Elemental Times

• Time standards derived from a firm’s historical data.

• Steps for standard elemental times

• Analyze the job

• Check file for historical times

• Modify file times if necessary

• Sum elemental times to get normal time

PMTS

At the "precision" end of the scale is a group of methods known as predetermined motion

time systems that use measurement units in ten thousandths (0.0001) of a minute or

hundred-thousandths of an hour (0.00001 hour).

The resulting standard times can be used directly, for very short-cycle work of around one

minute total duration such as small assembly work. However, they often are used to

generate regularly used basic tasks such using assembling or disassembling nuts and bolts,

using a screwdriver and similar. Tasks of this type are filed as standard or synthetic data-

banks.

Definition:

PMT Systems are methods of setting basic times for doing basic human activities necessary

for carrying out a job or task.

The definition in BS 3138, Glossary of Terms Used in Work Study is: 'Tables of time data at

defined rates of working for classified human movements and mental activities. Times for an

operation or task are derived using precise conventions. Predetermined motion time data

have also been developed for common combinations of basic human movements and

mental activities'.

Background

The principle of analyzing work into into basic actions was first published by F. Gilbreth in

1920, as his Therbligs. The first commercial and internationally recognized system was

devised in the 1930's to circumvent the banning by the government of the United States

time study and the stop-watch as the means of measuring work performed on US

government contracts. It was devised by Quick, Malcolm and Duncan under the title Work-

Factor and appeared in 1938. Other methods followed, the main one, some ten years later,

being Methods-Time Measurement (MTM). Both systems share basic similarities but are

based on different standards of time.

Outline description of PMTS

The concept of PMTS is to analyse a job into its fundamental human activities, apply basic

times for these from tables and synthesize them into a basic time for the complete job. The

basic elements include the following:

� reach for an object or a location

� grasp an object , touching it or closing the fingers

around it

� move an object a specified distance to a specified place

� regrasp an object in order to locate it in a particular

way, usually prior to:

� release an object to relinquish control on it

Other elements for assembling to, or inserting an object into, its intended location.

For each of these actions basic times are tabled. For example, in Work-Factor the time unit

is one thousandth of a minute (the Work-Factor Time Unit) whereas in MTM the unit is one

hundred-thousandth of an hour (time measurement unit, tmu).

The times for basic actions are adjusted for other factors which take into account such

variables as:

� distances moved, in inches or centimetres

� difficulty in performing the actions, such as avoiding

obstacles during moves, closeness of fit during

assembling, weight of the object, all of which increase

the times to carry out the basic actions.

The above basic motions cover most of the actions performed by humans when carrying out

work. Other basic activities include:

� walking to a specified place

� bending down and stooping

� kneeling on one knee and kneeling on both knees

� foot and leg motions

� sitting down and standing.

Mental activities include times for: See, Inspect, Identify, Nerve Conduct, React, Eye focus,

Eye travel times, Memorize, Recall, Compute (calculate) and others, mostly from Work-

Factor.

Levels of detail in systems

In order to speed up measurement time the major systems all include different levels of

detail, such as:

� Most detailed systems: MTM and Detailed Work-Factor

� Second level systems: MTM-2 and Ready Work-Factor

(abridged versions) achieved usually by the four

methods of combining, statistically averaging,

substituting and/or eliminating certain basic motions.

� Third level systems: MTM-3 and Abbreviated Work-

Factor (even more abridged)

� "higher level" systems, usually times for complete

activities.

One example of simplifying in the second level system MTM-2 is the combining of MTM

elements reach, grasp and release to produce a new MTM-2 element of "Get".

PMTS is often used to generate synthetic data or (standard data banks) which are overall

basic times for more complex tasks such as maintenance or overhauling of equipment. This

is achieved by synthesizing the hundreds of small jobs measured using PMTS into a time for

the complete project.

Basic times produced by PMTS need to have relaxation allowances and other necessary

allowances added to produce standard times.An example of part of a typical analysis in

MTM-2 is given.

An extract from an MTM analysis showing the first seven elements.

MTM Analysis

Job description: Analyst: E J H

Assemble r.f.

transformer to base-

plate

Date: 03-May

El. Description LH TMU'S RH Description

1 Move hand to washer R14C 15.6 R14B Move hand to

transformer

2 Grasp first washer G4B 9.1 G1A Grasp transformer

3 Move hand clear of

container M2B --- --- Hold in box

4 Palm washer G2 5.6 --- Ditto

5 To second washer R2C 5.9 --- Ditto

6 Grasp washer G4B 9.1 --- Ditto

7 Move washers to area M10B 16.9 M14C Transformer to plate

Notes on descriptions of some of the codes as examples.

The codes in the LH and RH columns refer to those in the MTM time tables. For example:

R14C is translated as "Reach 14 in. to an object jumbled with other objects in a group, so

that search and select occur" (Class C reach). R14B is translated as "Reach 14 in. to a single

object in location which may vary slightly from cycle to cycle." G2 is a grasp Case 2 which is a

regrasp to move the washer into the palm G4B is a Grasp Case 4B which is for grasping

*object jumbled with other objects so search and select occur. Objects within the range

0.25 x 0.25 x 0.125 in. to 1 x 1 x 1 inch."

One tmu is one hundred-thousandth of an hour

Estimating.

At the other end of the scale (long-cycle and project work) we need something which is

quick to use. Such a method is estimating. This can exist in three main forms.

a. Analytical estimating. Relies on the experience and judgement of the estimator. It is just of

case of weighing up the work content and, using this experience, stating a probable time for

completion, such as "this job will take about eight days to complete".

b. Category estimating. This is a form of range estimating and requires a knowledge of the

work. Estimators may not feel comfortable with overall, analytical estimates upon which

may depend the outlay of a great deal of money. They often prefer giving a range estimate

such as "this job should take between 12 weeks and 14 weeks to complete", which provides

a safety net should things go wrong. Such ranges are not just picked upon at random but are

statistically calculated and based on probability theory.

c. Comparative estimating. This is another example of range estimating. Again, estimators rely

on experience of the work in order to produce estimates. This experience can be augmented

by the provision of each time-range with a few typical, descriptive, jobs that would guide

estimators to the most appropriate range. The estimator would compare the work to be

estimated with those in the various ranges until the most appropriate fit is found.

Analytical Estimating In details

What is it?

Analytical estimating is a structured work measurement technique. The formal defination

states that it is a development of estimating, in which the time required to perform each

constituent part of a task at a defined rate of working is estimated from knowledge and

practical experience of the work and/or from synthetic data.

An important feature of this technique, which helps to improve accuracy, is that a whole job

should be broken down into smaller individual tasks. This is because any errors in the time

estimates may be seen as random and will therefore compensate for each other.

How can it be used?

Analytical estimating would normally be used for assessing work over a reasonably lengthy

period of time, where it may be difficult and more expensive to collect the information

required using other measurement techniques. Also, in some work environments the

presence of an individual carrying out work measurement in the work place could be

unacceptable. In these cases, analytical estimating may be an appropriate method to use,

assuming someone with experience of the work is available to apply their experienced

judgment. (This may be work measurement personnel who have previous experience of this

particular work )

However, the work content of some jobs cannot be estimated in advance because one is

unclear about what is required until an assembly operation has been tested or stripped

down. For example, during the progress of repair unforeseen and non standard difficulties

can arise. Removing a wooden door from its frame by unscrewing 8 or 12 screws could take

five minutes if the screws were recently inserted, or a great deal longer if the screws are

rusted and clogged with paint.

In summary, the technique is used most commonly in any work environment where a

lengthy time (and associated high cost) is needed to collect data.

Advantages & Disadvantages

Perhaps the most significant advantage of using analytical estimating is its speed of

application and low cost. Using trained and experienced personnel process and

measurement data can be quickly assembled and applied.

However, the use of experienced judgment when determining the time necessary to

perform a task is the technique's most obvious source of weakness when compared with a

more precise technique such as time study. This is why the technique would not normally be

used when a more precise and accurate alternative is a feasible and economic alternative,

particularly to highly repetitive, standardized operations. Many jobs, such as craft work in

the maintenance field, consist of a group of tasks which are periodically repeated but the

precise nature of each task varies each time in minor respects ( see research on Natural &

Normal Variation for further explanation). In this example, since it is impractical, in terms of

time and cost, to allocate one time study observer permanently to each craftsman, the

alternative is to use a time-study basis plus the experienced judgment of an ex-craft work-

study observer to allow for detailed task variations.

Work Sampling --- Assessing the Reasonableness of Labour Costs

Contractors develop labour estimates and budgets based on incurred labour cost history. If

these costs reflect inappropriate activities, they are not a reasonable basis for estimating

future costs. Typically, auditors perform two significant audits to determine whether

incurred labour costs are allocable and reasonable. These audits are:

a. Labour allocation audits that determine whether the contractor's workers are

charging the activities to which they are actually assigned.

b. Work sampling which determines whether, while assigned and charging to a

specific task, the workers are actively performing the task.

The typical DCAA work sampling audit does not formally assess worker effectiveness or

efficiency. Its primary concern is whether the work force is working.

Work Sampling --- An Application of Statistical Sampling

The statistical basis for work sampling is the same as that for the statistical sampling

methods discussed in Appendix B. The observations to be made must be selected randomly

and the observations themselves must be free of bias (measurement or observation errors

that tend to run in the same direction). If these conditions are met, the sample results will

differ from the actual conditions only in a random manner and will thus be unbiased.

Furthermore, the greater the number of observations, the more closely will sample results

approximate actual conditions.

Work sampling can enhance auditor productivity. Worker activities, like records or items in

an account or bill of materials, can be sampled instead of being totally or continuously

audited.

Advantages, Terminology, and Software

a. Some of the primary advantages of work sampling are as follows:

(1) Sampling is less expensive than continuous observation techniques.

(2) Observers with minimal specialized training can conduct the sampling.

(3) The number of observations can be adjusted to meet desired levels of precision.

(4) Sampling is an effective means of collecting facts that would not normally be collected by

other means.

(5) Sampling results in less anxiety and agitation among workers than continuous

observation.

(6) There is minimal interference with the worker's normal routine.

b. An understanding of the principal work sampling terms is necessary to use this guidance

and work sampling software. Key terms and their definitions are as follows:

(1) SURVEY AREA (Universe): the total of all workers or machines to be covered in the

survey.

(2) PRELIMINARY SURVEY (Probe): the preliminary "work/no-work" observations are

conducted to determine the general amount of nonworking in the survey area. This survey

helps to estimate the approximate number of observations that will be required for the

work sampling audit. Additionally, the preliminary survey aids in identifying the categories

of nonworking activity.

(3) PRELIMINARY POINT ESTIMATE: the preliminary estimate of nonworking activity

determined either by the preliminary survey (probe) or past experience.

(4) KNOWLEDGE WORKERS: those workers whose output is mostly intangible (e.g.,

accountants, engineers, clerks, etc.). Often referred to as non touch workers.

(5) PHYSICAL WORKERS: those workers whose output is mostly tangible (e.g., welders,

machinists, assemblers, etc.). Often referred to as touch workers.

(6) GROUP SAMPLING: a method in which groups of workers are collectively observed at

randomly selected areas and times.

(7) INDIVIDUAL SAMPLING: a method in which the workers are randomly selected and

individually observed at randomly selected times.

(8) OBSERVATION TOUR (Round): a tour performed at a specific time to determine the work

classification of an individual worker or a group of workers.

(9) OBSERVATION: the recorded results of an individual or group sampling observation tour.

An example of a group observation is: 5 working, 3 non working (2 non business talking, 1

reading newspaper).

(10) OBSERVATION TIME: a randomly selected start time for initiating an observation tour.

(11) NONWORKING ACTIVITY: that effort which does not contribute to the output of the

operation. Eating and non business talking are examples of nonworking activity.

(12) WORKING ACTIVITY: that effort which directly or indirectly contributes to the output of

the operation. Assembling and designing are examples of working activity.

(13) UNDESIRABLE WORKING ACTIVITY: an activity that is classified as working but can be

eliminated or reduced by improved procedures. Examples include walking, waiting, cleaning,

etc.

(14) CONFIDENCE LEVEL: the chance (or probability) that the true universe value that is

being estimated by the sample is included in a specified range (see item (15) below). In

evaluation of sample results, the desired confidence level is specified by the sampler and

the precision range is computed accordingly. In sample size determination, both the desired

confidence level and the desired precision range are specified, and the sample size is

computed accordingly. For example, if the desired confidence level is 95 percent and the

precision range computed from the sample results is from 12 to 18 percent nonworking,

there is a 95 percent chance that the true nonworking is between 12 and 18 percent.

Normal desired confidence levels are 90 or 95 percent.

(15) PRECISION RANGE: a range of possible universe values that is determined according to

the confidence level (see item (14) above). When computed from sample results to meet a

specified confidence level, the precision range consists of an upper and lower limit. In

sample size determination, the desired precision range (sometimes referred to as desired

precision) is specified along with the desired confidence level. It does not depictan upper

and lower limit, but instead it consists of a desired limit on the amount by which the sample

point estimate might differ from the true universe value. In work sampling desired precision

ranges are typically 6 percent (3 percent).

c. Microcomputer software (WSAMP2) to appraise work sampling results is available on

floppy diskette. Information necessary to use the software is contained within the program,

and is available as a menu option. The program computes the average percentage of

nonworking activity, related precision ranges, and estimates of the number of observations

required to achieve desired precision at various confidence levels. In addition, the program

can be used to analyze causes, areas, and timeframes of nonworking activity. The program

has two options. Option 1 analyzes group sampling results, and option 2 analyses individual

sampling results

Activity Sampling

What is it?

Activity Sampling is a statistical technique that can be used as a means for collecting data. It

is defined by as:

A technique in which a large number of observations are made over a period of time of one

group of machines, processes or workers. Each observation records what is happening at

that instant and the percentage of observations recorded for a particular activity or delay is

a measure of the percentage of time during which that activity or delay occurs.

It is normally used for collecting information on the percentages of time spent on activities,

without the need to devote the time that would otherwise be required for any continuous

observation.

One of the great advantages of this technique is that it enables lengthy activities or groups

of activities to be studied economically and in a way that produces statistically accurate

data.

Fixed and Random Interval Sampling

Activity Sampling can be carried out at random intervals or fixed intervals. Random activity

sampling is where the intervals between observations are selected at random e.g. from a

table of random numbers. Fixed interval activity sampling is where the same interval exists

between observations. A decision will need to be made on which of these two approaches is

to be chosen. A fixed interval is usually chosen where activities are performed by a person

or group of people who have a degree of control over what they do and when they do it.

Random intervals will normally be used where there are a series of automated tasks or

activities as part of a process, that are have to be performed in a pre established regular

pattern. If fixed interval sampling were to be used in this situation there is a danger that the

sampling point would continue to occur at the same point in the activity cycle.

Confidence Levels

Remember, that activity sampling is used for assessing the percentage of time spent on

activities.

Because activity sampling conforms to the binomial distribution it is possible to use a

calculation to determine how many observations will be needed to operate within specified

limits of accuracy.

The formula for the number of observations is as follows:

= 4 x p x (100 - p)

L2

Where p is the estimated % time spent on the activity

Where L is the limit of error, expressed as a %

Once the above calculation has been completed the observations can begin and activities

are recorded at the agreed time intervals. When they have been completed a further

calculation can be used to determine the error rate, as follows:

Error Rate = ± 2 x √( p x (100 - p) )

Number of observations

This is very much an overview to the topic of activity sampling, with a definition of what it is,

its advantage over continuous observation and the formulae that can be used to establish

the confidence levels that can be obtained.

Procedure of Analytical Estimating

The various steps involved are:

1. Find out the job details such as job dimension, standard procedure to do the job, and the

job conditions, such as poor illuminated, high temperature, hazardous environments,

availability of jigs, fixture or tools, etc.

2. Break the job into its elements.

3. Select time values from the standard data catalogue for as many elements as possible.(i.e.

use synthetic data wherever available)

4. Estimate the time values for the remaining elements(for which synthetic data is not

available) from past knowledge and experience.

5. Add the time values obtained by steps 3 and 4 to get the total ‘Basic’ or ‘Normal’ time(for

100% rating) 6.Add the appropriate blanket relaxation allowance (say 10% to 20% of total

normal or basic time)Note that in analytical estimating, the relaxation allowance is not

added to time values of individual elements. The blanket relaxation allowances depends on

the type of the job and the job conditions.

7. Add any other allowances if applicable, to arrive at the standard time for the given job.

Advantages of Analytical Estimating Technique

(i) Offers the same advantages enjoyed by synthesis method.

(ii) Helps in planning and scheduling the production

(iii) Provides a basis for fixing the labor rate for non-repetitive jobs.

(iv) Steps to improve labor control.

Disadvantages

Since analytical estimating technique relies upon the judgment of the estimator, the time

values obtained may not be as accurate and reliable as that estimated by the stop-watch

time study.

Applications of Analytical Estimating Technique

(i) For non-repetitive jobs, jobs having long cycle times and jobs having elements of variable

nature. For such jobs the stop-watch time study proves to be uneconomical.

(ii) For repair and maintenance work, job production, one time large projects, office

routines, tool room jobs and engineering construction works.

Category estimating. This is a form of range estimating and requires a knowledge of the

work. Estimators may not feel comfortable with overall, analytical estimates upon which

may depend the outlay of a great deal of money. They often prefer giving a range estimate

such as "this job should take between 12 weeks and 14 weeks to complete", which provides

a safety net should things go wrong. Such ranges are not just picked upon at random but are

statistically calculated and based on probability theory.

Comparative estimating. This is another example of range estimating. Again, estimators rely

on experience of the work in order to produce estimates. This experience can be augmented

by the provision of each time-range with a few typical, descriptive, jobs that would guide

estimators to the most appropriate range. The estimator would compare the work to be

estimated with those in the various ranges until the most appropriate fit is found.

Models:

A most useful method for standard or synthetic data-banks of job or element times is using

computer models of the jobs. These are generated as mathematical formulae in which the

observed data are inserted to compile a time for completion of the task or project. It is a

useful method for recycling time standards for elements of basic work over and over again,

only changing the values of the variables to suit each project.

Work Measurement Components

A work measurement system has three components: preferred methods, time values, and

re porting. Preferred methods are not always the most efficient or fastest way to do a task.

They should enhance safety, quality, and productivity. Safety for the employee and for the

product should be considered. Quality is equally important; it has been proven that good

performance and good quality go hand in hand. People who are trained in the proper

method and follow that method will produce high-quality work and per form at an

acceptable performance level. Time values and reporting should also be considered. The

time that a job should take is determined not on the basis of speeding up the motions a

worker normally makes but on the normal pace of the average worker, taking into

consideration allowances for rest periods, coffee breaks, and fatigue. A reporting system is

important to the success of any work measurement method. Supervisors and managers

must have access to labour-management information that is both timely and complete.

Timely information can be used to manage and shift labour hours to areas where they are

needed and to correct problems or at least prevent them from becoming a crisis. Personal

computers help to apply work measurement more effectively and more cheaply and provide

immediate feedback to the workers, supervisors, and managers.

Application of Work-Measurement

Application of Work-Measurement Analysis to Product Disassembly for Recycling

A method for evaluating the ease of disassembly of products is introduced Its primary use is

in designing products for recycling and making environmentally-related decisions, but it is

also relevant to servicing and maintenance The evaluation procedure

is centred around a

spreadsheet-like chart and uses a catalogue of task difficulty scores The scores were derived

from work-measurement analyses of standard disassembly tasks and provide a means of

identifying weaknesses in the design and comparing alternatives

quantitatively The

procedure of applying work-measurement analysis to disassembly tasks is described and

demonstrated in detail A relatively simple example of disassembly evaluation of a computer

drives assembly illustrates the use of the method and its implementation as a design tool.