GROUP- 3

To

Our presentation

members

Tonima Khan Parvej Ahmed Dipok Kumar Das Namira Sultana Shahidul Islam Asaduzzaman Oni Ahmedullah Ahmed

Mostafizur Rahman Subroto Kumar Mahabub Rahman Shakhawat Hossain Samson Tudu Abu Sadat Md. Sakib

Namira Sultana

Roll: 7038

Topic: Census

Census

A census is the procedure of systematically acquiring and recording information about the members of a given population.

It is a regularly occurring and official count of a particular population.

The term is used mostly in connection with national population and housing censuses; other common censuses include agriculture, business, and traffic censuses.

A survey that measures the entire target population is called a census.

Tonima Khan

Roll: 7001

Topic: Sample

What is Sample

A sample is a subset of the population.

It comprises some members selected from it. In other words, some, but not all, elements of the population would form the sample.

According to E.R Babble “A sample is a special subset of population that is observed for purpose of making inference about the nature of the total population itself .”

Example if there are 145 in-patients in a hospital and 40 of them are to be surveyed by the hospital administrator to assess their level of satisfaction with the treatment received, then these 40 members will be the sample.

Mahbubur Rahman

Roll: 7127

Topic: Sampling survey

The sample survey was only a small size but it did give us a window of knowledge and understanding . The sample survey that we gave to the public was given in order to determine what we needed to do.

A sample survey can often change the design of a product or

even the entire product as a whole, depending on current consumer opinions.

Sampling Survey

According to the black and champion- “The process of drawing those elements from the larger population or universe is called sampling”

According to the bhandarker- “The method of selecting for study a portion of the universe with a view to drawing conclusion about the universe is know as sampling.”

Sampling is to reduce the cost or the amount of work that it would take to survey the entire target population.

Parvej Ahmed

Roll: 7012

Topic: Census Vs. Sample survey

In Census, each and every unit of population is studied. But only few units of the population studied is studied in Sampling.

Census refers to periodic collection of information about the populace from the entire population.

However, if the next Census is far away, Sampling is the most convenient method of obtaining data about the population.

Census Method demands a large amount of finance, time and labor. Relatively less amount of finance, till labor is required for sampling.

Difference between Census and sampling

Difference between Census and sampling

Results obtain by the Census are quit reliable. Results obtained by the Sampling are less reliable.

It is more suitable to use Census Method if population is heterogeneous in nature.

and it is more suitable to use Sampling Method if population is homogeneous in nature.

Samples have a margin of error though, which gets lower as the sample size increases. In other words sampling more people means obtaining better data.

Instead, this type of error not present in Census as each and every part of the geographical area has to be approached for data collection .

Samson Tudu

Roll: 7140

Topic: Sample Design

A sample design is the framework, or road map, that serves as the basis for the selection of a survey sample and affects many other important aspects of a survey as well.

In broad context survey researchers are interested in obtaining some types of information through a survey for some population or universe. One must define a sampling frame that represents the population of interest from which a sample is to be drawn.

Sample Design

Preparing a sample design:

1. Types of universe (set of objects) /finite or non finite

2. Sample unit (district, school, age)3. Sampling frame4. Size of sample5. Sampling technique

Abu Sadat Md. Sakib

Roll: 7143

Topic: Characteristics of Good Sample Design

Following are the characteristics of good sample design:

1. Sample design should be a representative sample: A researcher selects a relatively small number for a sample from an entire population. If the sample used in an experiment is a representative sample then it will help generalize the results from a small group to large universe being studied.

2. Sample design should have marginal systematic bias: Systematic bias results from errors in the sampling procedures which cannot be reduced or eliminated by increasing the sample size. The best bet for researchers is to detect the causes and correct them.

3. Results obtained from the sample should be generalized and applicable to the whole universe: The sampling design should be created keeping in mind that samples that it covers the whole universe of the study and is not limited to a part.

4. Sample design should have small sampling error:Sampling error is the error caused by taking a small sample instead of the whole population for study. Sampling error refers to the discrepancy that may result from judging all on the basis of a small number. Sampling error is reduced by selecting a large sample and by using efficient sample design and estimation strategies.

5. Sample design should be economically viable: Studies have a limited budget called the research budget. The sampling should be done in such a way that it is within the research budget and not too expensive to be replicated.

Conti….

Sahidul Islam Suzan

Roll:7058

Topic: Importance of Having Good Sample Design

Importance of Having Good Sample Design

Efficient business research : Sample research design is a pre-condition of business research. If we want to make our business research efficient we should make proper use of sample design.

Cost minimization: As a principle of minimization cost in every research project we should prepare a sample design at first.

Backbone of Research: Sample design is just like CPU and brain of a research. Because when we prepare a research design we will collect information from sample design.

Smooth running of business : If we want to run the activities of business continuously we need a research design and this research design is totally dependent on sample design.

Shakhawat Hossain

Roll: 7125

Topic: Importance of Having Good Sample Design

EFFICIENCY IN SAMPLING Efficiency in sampling is attained when for a given level of precision (standard

error), the sample size could be reduced, or for a given sample size (n), the level of precision could be increased.

Some probability sampling designs are more efficient than others.

The simple random sampling procedure is not always the most efficient plan to adopt; some other probability sampling designs are often more efficient.

A stratified random sampling plan is often the most effi- cient, and a disproportionate stratified random sampling design has been shown to be more efficient than a proportionate sampling design in many cases.

Importance of Having Good Sample Design

MANAGERIAL RELEVANCE Awareness of sampling designs and sample size helps managers to understand why a

particular method of sampling is used by researchers.

It also facilitates understanding of the cost implications of different designs, and the trade-off between precision and confidence vis-à-vis the costs.

This enables managers to understand the risk they take in implementing changes based on the results of the research study.

While reading journal articles, this knowledge also helps managers to assess the generalizability of the findings and analyze the implications of trying out the recommendations made therein in their own system.

Cont…..

Mostafizur Rahman

Roll: 7074

Topic:Factors considered in sample design

The researcher have to consider the following factors while preparing a sample design.

1.Universe: While preparing a sample design, it is required to define the set of objects to be studied. Technically, it is also known as the Universe, which can be finite or infinite.

2.Sampling unit: It is necessary to decide a sampling unit before selecting a sample design. It can be a geographical one (state, district, village, etc.), a construction unit (house, flat, etc.), a social unit (family, club, school, etc.), or an individual.

3 Sample size: Whether you are using a probability sampling or non-probability sampling technique to help you create your sample, you will need to decide how large your sample should be (i.e., your sample size). . The sample size should not be too large or too small, but optimum. Your sample size becomes an ethical issue for two reasons: (a) Over-sized samples and (b) under-sized samples.

Factors considered in sample design

4. Source list: In other words, it is called the ‘sampling frame’ from which the sample is drawn. It is a list of the items or people forming a population from which a sample is taken. . If source list/sampling frame is unavailable, the researcher has to prepare it by himself.

5. Parameters of interest: While determining a sample design, it is required to consider the question of the specific population parameters of interest.

6. Budgetary constraint: Practically, cost considerations have a major impact upon the decisions concerning not only the sample size but also the sample type.

7. Sampling procedure: The researcher, at last, decides the techniques to be used in selecting the items for the sample. In fact, this technique/procedure stands for the sample design itself. So such a design should be selected, which for a provided sample size and cost, has a smaller sampling error

Factors considered in sample design

Dipok Kumar Das

Roll:7024

Topic:Types of Sample Design

Types of sample designProbability

samples

Non-probability samples

Each element or each combination of elements has equal probability of selection.

Applicable when population is small , homogeneous & readily available.

A table of random number or lottery system is used to determine which are to be selected

Simple Random Sampling Design

Systematic sampling relies on arranging the target population according to some ordering scheme & then selecting elements at regular intervals.

Each element has equal probability of selection but combination of elements have different probabilities.

Population size N, desired sample size n , sampling interval k=N/n.

Randomly select a number j between 1 & k ,sample element j & every kth element thereafter j+k,j+2k etc.

Example: N=64,n=8, k=64/8=8.now assume j=3.Here starting with case number chosen in j=3 & taking

every 3rd number recode(such as 3,11,19 etc).

Systematic Sampling Design

Subroto kumar

Roll: 7104

Topic: Cluster sampling and stratified sampling

Where population embraces a number of distinct categories then the population is broken down into separate groups in which each group is sampled as sub-population & a random sample is taken of each category.

Every unit in a group has same chance of being selected.

Probabilities of selection may be different for different groups.

Stratified Sampling Design

Cluster sampling is a sampling technique used when "natural" but relatively homogeneous groupings are evident in a statistical population.

It is often used in marketing research. In this technique, the total population is divided into these groups (or clusters)

and a simple random sample of the groups is selected.

Cluster sampling

Ahmedullah Ahmed

Roll:7054

Topic: Types of Sample Design

Complex form of cluster sampling in which two or more levels of units are embedded one in the other.

First stage, random number of districts chosen in all states.

Followed by random number of talukas , villages.

Then third stage units will be houses

This technique, is essentially the process of taking random samples of preceding random samples.

Multistage sampling used frequently when a complete list of all members of population not exists is appropriate.

Multistage sampling

In multiphase sampling the different phase of observations relate to the sample units of the same type.

Part of the information collected from sample & subsample .

Survey by such procedure is less costly , less laborious & more purposeful

Multiphase sampling :

Md. Asaduzzaman Oni

Roll: 7051

Topic: Non probability Sampling

Convenience Sampling

Sometimes known as grab or opportunity sampling or accidental or haphazard sampling.

A type of non probability sampling which involves the sample being drawn from that part of the population which is close to hand. That is, readily available and convenient.

Cont….

Purposive sampling:

the process whereby the researcher selects a sample based on experience or knowledge of the group to be sampled

…called “purposive” sampling

The researcher chooses the sample based on who they think would be appropriate for the study.

This is used primarily when there is a limited number of people that have expertise in the area being researched.

Judgmental Sampling

Cont…

Can not scientifically make generalization about the total population from this sample because it would not be representative enough

The population is first segmented into mutually exclusive sub-groups, just as in stratified sampling.

Then judgment used to select subjects or units from each segment based on a specified proportion.

For example, an interviewer may be told to sample 200 females and 300 males between the age of 45 and 60.

QUOTA SAMPLING

The problem is that these samples may be biased because not everyone gets a chance of selection. This random element is its greatest weakness and quota versus probability has been a matter of controversy for many years

Cont……