Ag engineering PE review: Exam prep, I-C economics and statistics

Ag engineering PE review: Ag engineering PE review: Exam prep, I-C economics and Exam prep, I-C economics and

statisticsstatistics

Marybeth Lima, Ph.D., P.E.Marybeth Lima, Ph.D., P.E.Cliff & Nancy Spanier Alumni Cliff & Nancy Spanier Alumni

ProfessorProfessorBiological & Agricultural Biological & Agricultural

EngineeringEngineeringE-mail: [email protected]: [email protected]

OverviewOverview

““Use of your PE reference books” Use of your PE reference books” exerciseexercise

Economic analysis and statistics (we’ll Economic analysis and statistics (we’ll do hypothesis testing Thursday)do hypothesis testing Thursday)

ThroughoutThroughout: : You will be doing PE style problems (have You will be doing PE style problems (have

your references and calculators ready!)your references and calculators ready!) Ask questionsAsk questions

Part 1: Exam Part 1: Exam preparationpreparation

References (must have)References (must have) Time (in preparing for exam and Time (in preparing for exam and

during exam)during exam) Strategies (preparation and test Strategies (preparation and test

taking)taking)

ReferencesReferences Are an absolutely critical part of your Are an absolutely critical part of your

preparation; you will not pass the exam preparation; you will not pass the exam without the proper referenceswithout the proper references

There is a comprehensive list of There is a comprehensive list of references in the booklet entitled “A references in the booklet entitled “A Guide to Professional Licensure for Guide to Professional Licensure for Agricultural, Food, and Biological Agricultural, Food, and Biological Systems Engineers.”Systems Engineers.” http://www.asabe.org/pei/index.htmlhttp://www.asabe.org/pei/index.html

Some references are more useful than Some references are more useful than othersothers

References I used for 80% References I used for 80% of the exam problems (must of the exam problems (must

haves)haves) A Guide to Professional Licensure for Agricultural, A Guide to Professional Licensure for Agricultural,

Food, and Biological Systems EngineersFood, and Biological Systems Engineers The notes from this on-line review course (bound)The notes from this on-line review course (bound) ASAE Standards (I used the 2000 edition for the 2005 ASAE Standards (I used the 2000 edition for the 2005

exam and was fine)exam and was fine) The Civil Engineering Reference Manual for the PE The Civil Engineering Reference Manual for the PE

exam (soil and water, wastewater, pumps, econ tables, exam (soil and water, wastewater, pumps, econ tables, INDEX)INDEX)

The Mechanical Engineering Reference Manual for the The Mechanical Engineering Reference Manual for the PE exam (HVAC, machine systems, econ tables, fans, PE exam (HVAC, machine systems, econ tables, fans, INDEX)INDEX)

You don’t have to bring both PE manuals but have one; I’d You don’t have to bring both PE manuals but have one; I’d recommend civil over mechanical because of broad coverage recommend civil over mechanical because of broad coverage of topics. If you pick the civil manual, bring ASHRAE of topics. If you pick the civil manual, bring ASHRAE Fundamentals or another strong HVAC book.Fundamentals or another strong HVAC book.

Other references I usedOther references I used Wastewater Engineering, Metcalf and Eddy Wastewater Engineering, Metcalf and Eddy

(used 3(used 3rdrd edition) edition) Henderson, Perry and Young, Principles of Henderson, Perry and Young, Principles of

Process EngineeringProcess Engineering Wood Engineering, Gurfinkel (any wood Wood Engineering, Gurfinkel (any wood

engineering book will do; you need the tables engineering book will do; you need the tables at the back; you may find in civil vs. ag parts at the back; you may find in civil vs. ag parts of library)of library)

A soil physics bookA soil physics book MWPS-1: Structures and Environment MWPS-1: Structures and Environment

Handbook (op)Handbook (op) Schwab et al. Soil and water conservation Schwab et al. Soil and water conservation

engineering (4engineering (4thth edition) edition)

References I brought and References I brought and did not usedid not use

Irrigation SystemsIrrigation Systems NRCS handbook parts 650 and 651NRCS handbook parts 650 and 651 Goering and Hansen, Engine and tractor Goering and Hansen, Engine and tractor

powerpower Shuler and Kargi, Bioprocess Shuler and Kargi, Bioprocess

Engineering Basic ConceptsEngineering Basic Concepts Salvendy, Handbook of Human FactorsSalvendy, Handbook of Human Factors MWPS-8, Swine Housing and Equipment MWPS-8, Swine Housing and Equipment

Handbook Handbook

Time: preparing for the Time: preparing for the examexam

Get your references and get used to using them (tab Get your references and get used to using them (tab Standards)Standards)

Make an index of where specific information is Make an index of where specific information is located so that you don’t have to search during located so that you don’t have to search during the examthe exam

Do and re-do all the problems you are given in the on-Do and re-do all the problems you are given in the on-line courseline course

Do problems in your reference books (especially A Do problems in your reference books (especially A Guide to Professional Licensure for ag, food and bio Guide to Professional Licensure for ag, food and bio engineers)engineers)

Focus your time: general ag engineering knowledge, Focus your time: general ag engineering knowledge, your expertise area, your secondary knowledge areasyour expertise area, your secondary knowledge areas

Don’t spend time on what you KNOW you won’t touch Don’t spend time on what you KNOW you won’t touch (there is something you won’t)(there is something you won’t)

The week before the test, do a sample test using the 8 The week before the test, do a sample test using the 8 hr exam format (road test caffeine issues, etc.)hr exam format (road test caffeine issues, etc.)

Time during the examTime during the exam The exam is designed such that each question The exam is designed such that each question

takes an average of six minutestakes an average of six minutes There are 1 minute problems and 15-20 minute problemsThere are 1 minute problems and 15-20 minute problems

Go through the test and answer questions in the Go through the test and answer questions in the following order:following order: The quick, easy ones that you know you can doThe quick, easy ones that you know you can do The ones you know that you can do that take a little more The ones you know that you can do that take a little more

timetime Guess (with gusto!) at the ones that are beyond your scopeGuess (with gusto!) at the ones that are beyond your scope

Guess the same letter every timeGuess the same letter every time Go back and do the ones that you think you can do that are Go back and do the ones that you think you can do that are

time consumingtime consuming If there’s time, go back and check your answers; also go to If there’s time, go back and check your answers; also go to

the ones that are bugging you (if there are any)the ones that are bugging you (if there are any)

StrategiesStrategies You need to develop problem recognition You need to develop problem recognition You need to develop flexible thinkingYou need to develop flexible thinking Pick what you will not answer and guess with Pick what you will not answer and guess with

pleasure (I guessed at 10% of the questions on the pleasure (I guessed at 10% of the questions on the exam)exam)

Many times you can eliminate two of the four choices Many times you can eliminate two of the four choices easily (even with areas you know nothing about)easily (even with areas you know nothing about)

The sample exam in the licensure book was very The sample exam in the licensure book was very much like the actual exam in terms of format and much like the actual exam in terms of format and somewhat alike in terms of types of problems somewhat alike in terms of types of problems The exam doesn’t specify which section is which, but you’ll have The exam doesn’t specify which section is which, but you’ll have

four or five consecutive questions that are from the same area and four or five consecutive questions that are from the same area and then on to the next area)then on to the next area)

Knowing fundamental knowledge is critical (the PE Knowing fundamental knowledge is critical (the PE reference manuals in civil and mechanical were reference manuals in civil and mechanical were invaluable)invaluable)

StrategiesStrategies

You need to answer ~60% of the problems You need to answer ~60% of the problems correctly to passcorrectly to pass Having a strong base in general agricultural Having a strong base in general agricultural

engineering knowledge will “take you over the top”engineering knowledge will “take you over the top” My experience: for the various expertise areas, My experience: for the various expertise areas,

about 60% of the problems were solvable without about 60% of the problems were solvable without expert knowledge in the area (as long as you had expert knowledge in the area (as long as you had good references and knew where to look for info)good references and knew where to look for info)

The other 40% of the expertise questions were The other 40% of the expertise questions were expert knowledge level, involved problems (I expert knowledge level, involved problems (I skipped P&M, irrigation, and skipped P&M, irrigation, and structures/environment expert problems)structures/environment expert problems)

““Use of your PE reference books” Use of your PE reference books” exerciseexercise

On the PE exam, you want the “1 minute questions” On the PE exam, you want the “1 minute questions” that appear on the test to take 1 minute to answerthat appear on the test to take 1 minute to answer

These questions are testing your basic knowledge These questions are testing your basic knowledge of the field and your ability to bring and use the of the field and your ability to bring and use the proper referencesproper references

Practice: find the answers to the questions on the Practice: find the answers to the questions on the following slidesfollowing slides ApproachApproach

First, classify the problem: in which area of the Ag PE do you First, classify the problem: in which area of the Ag PE do you think the problem is contained? In which references might think the problem is contained? In which references might you find the information?you find the information?

When you find the answer, record the value, the reference in When you find the answer, record the value, the reference in which you found the answer, AND descriptive information which you found the answer, AND descriptive information within the reference (page number, table number, figure within the reference (page number, table number, figure number, equation number, etc.)number, equation number, etc.)

Question 1Question 1

What is the heat of combustion of What is the heat of combustion of propane?propane?

NOTE: heat of combustion is also NOTE: heat of combustion is also referred to as heating valuereferred to as heating value

Heat of combustionHeat of combustion


The Atterburg limit test measures The Atterburg limit test measures what?what?


What is the Young’s modulus of What is the Young’s modulus of elasticity of stainless steel?elasticity of stainless steel?


What is the density of air at 10° C?What is the density of air at 10° C?


What is the curve number for What is the curve number for contoured row crops in good contoured row crops in good hydrologic condition for hydrologic hydrologic condition for hydrologic soil group B?soil group B?


For a relatively uniform distribution For a relatively uniform distribution of soil particles 1 mm in diameter, of soil particles 1 mm in diameter, what is the largest sieve size that what is the largest sieve size that these particles would not pass these particles would not pass through?through?


What is the typical concentration of What is the typical concentration of suspended solids (SS) in septage?suspended solids (SS) in septage?


What is the equilibrium moisture What is the equilibrium moisture content of rough rice at 30° C and content of rough rice at 30° C and 80% RH?80% RH?

Questions on this Questions on this exercise?exercise?

In my experience, 10-20% of the In my experience, 10-20% of the questions on the exam were of this questions on the exam were of this naturenature Fast if you had the right references and Fast if you had the right references and

knew where to find the informationknew where to find the information

1-C: Economics and 1-C: Economics and statisticsstatistics

A broad area with applications “across the A broad area with applications “across the board” (5% of exam questions)board” (5% of exam questions) Statistics is commonly used because you need Statistics is commonly used because you need

descriptive information to help interpret datadescriptive information to help interpret data Economics is commonly used for making Economics is commonly used for making

engineering decisionsengineering decisions My suggestion for stats and econ: use the My suggestion for stats and econ: use the

CE or ME PE reference book (Lindeburg)CE or ME PE reference book (Lindeburg) Chapter on statistics Chapter on statistics

Table at the back (z-chart)Table at the back (z-chart) Get a t-chart as well!!Get a t-chart as well!!

Chapter on engineering economic analysisChapter on engineering economic analysis Full interest tables at the backFull interest tables at the back

Statistics basicsStatistics basics

Measures of central tendencyMeasures of central tendency Mean, median, modeMean, median, mode

Measures of dispersionMeasures of dispersion Standard deviation, variance, range, coefficient Standard deviation, variance, range, coefficient

of varianceof variance For PE: have equations to determine For PE: have equations to determine

measures of central tendency and dispersionmeasures of central tendency and dispersion There are slight differences in equations There are slight differences in equations

depending on if you are working with a depending on if you are working with a population or a samplepopulation or a sample

Statistics: DistributionsStatistics: Distributions

A number of distributions can be used A number of distributions can be used to describe various data sets or can to describe various data sets or can be used to solve engineering be used to solve engineering problems in relation to these data setsproblems in relation to these data sets Sampling distributions involving means:Sampling distributions involving means:

Normal (aka Gaussian): our focusNormal (aka Gaussian): our focus Student t distributionStudent t distribution

Sampling distributions involving Sampling distributions involving variance:variance:

F distributionF distribution Chi-SquareChi-Square

Normal distribution: Normal distribution: reviewreview

Symmetrical distribution with Symmetrical distribution with mean mean and standard deviation and standard deviation

Area under curve represents Area under curve represents 100% of possibilities100% of possibilities 50% to the right of the mean50% to the right of the mean 50% to the left of the mean50% to the left of the mean

A value is higher than the A value is higher than the mean for this distribution to mean for this distribution to the right of the mean, lower to the right of the mean, lower to the left of the meanthe left of the mean

x represents where you are in x represents where you are in the distribution; z is the the distribution; z is the number of standard deviations number of standard deviations away from the mean that you away from the mean that you areare z is positive to right of meanz is positive to right of mean z is negative to left of meanz is negative to left of mean

x

z

x

z

x

z

x

z

Reading the z-chartReading the z-chart

Typical PE style Typical PE style problemsproblems

The population mean for college The population mean for college students’ heights is 67 inches, and students’ heights is 67 inches, and the population standard deviation is the population standard deviation is and 4 inches. These data are and 4 inches. These data are normally distributed.normally distributed. What percentage of college students What percentage of college students

have heights less than 71 inches? have heights less than 71 inches?

)18.259.0( zP

SolutionSolution

In what range would you find the In what range would you find the middle 70% of the data? (pick closest z middle 70% of the data? (pick closest z value, do not interpolate)value, do not interpolate)

SolutionSolution

You try this one:You try this one:

90% of college students have heights 90% of college students have heights greater than what value?greater than what value?

SolutionSolution

SamplingSampling

We almost never work with populationsWe almost never work with populations We take samples and try to draw We take samples and try to draw

conclusions about a population based conclusions about a population based on a sampleon a sample Use z chart for large samples (n>30)Use z chart for large samples (n>30) Use t chart for small samplesUse t chart for small samples

Your statistical equations change a Your statistical equations change a little to reflect the fact that you have a little to reflect the fact that you have a samplesample

n

xz

x

z

Confidence intervalsConfidence intervals

Commonly used in research and Commonly used in research and process controlprocess control

95% confidence intervals are 95% confidence intervals are commoncommon

For example, what is the 95% For example, what is the 95% confidence interval of a set of 50 confidence interval of a set of 50 data points; the mean of this data set data points; the mean of this data set is 150 and the standard deviation is is 150 and the standard deviation is 15.15. z n

z

2

n

stx

2

SolutionSolution

Questions on statistics?Questions on statistics?

Tips: Tips: Get a general reference with equations Get a general reference with equations

and make sure you have a z chart and a and make sure you have a z chart and a t chartt chart get z from A, and A from zget z from A, and A from z Know confidence intervalsKnow confidence intervals Look at process control and hypothesis Look at process control and hypothesis

testingtesting

1-C: Engineering 1-C: Engineering economic analysiseconomic analysis

Typically easy questions on the exam if you know Typically easy questions on the exam if you know how to use factor tables (slang, interest tables)how to use factor tables (slang, interest tables) Tabulated in the ME reference manual, A-132-150 or CE Tabulated in the ME reference manual, A-132-150 or CE

manual A-112-130manual A-112-130 Types of problems in engineering economic analysisTypes of problems in engineering economic analysis

Decision making: you have a material you’re trying to Decision making: you have a material you’re trying to choose, or a part, or a machine. Compare which is most choose, or a part, or a machine. Compare which is most economical given present cost, maintenance costs, etc.economical given present cost, maintenance costs, etc.

Replacement/retirement analysis (when should you replace Replacement/retirement analysis (when should you replace or retire a product?)or retire a product?)

Rate of return problem (to find percentage return on an Rate of return problem (to find percentage return on an investment)investment)

Break even point on an investment Break even point on an investment Loan repayment (how long will it take)Loan repayment (how long will it take) Economic life analysis (life cycle costs)Economic life analysis (life cycle costs) Benefit/cost analysis (do the benefits outweigh the costs)Benefit/cost analysis (do the benefits outweigh the costs)

Engineering econEngineering econ Almost all engineering econ problems will involve Almost all engineering econ problems will involve

cashcash flowsflows; it is like a material balance using ; it is like a material balance using money instead of mass.money instead of mass.

Types of cash flows:Types of cash flows: Single payment cash flows (P or F)Single payment cash flows (P or F)

P = present value of moneyP = present value of money F = future value of moneyF = future value of money

Uniform series cash flow (A) Uniform series cash flow (A) An amount that is the same every month, like a house or car An amount that is the same every month, like a house or car

paymentpayment Gradient series cash flow (not used much) (G)Gradient series cash flow (not used much) (G)

A value that goes up or down the same amount every time A value that goes up or down the same amount every time periodperiod

You use types of cash flows to compare alternatives You use types of cash flows to compare alternatives and solve econ problemsand solve econ problems

Engineering econEngineering econ

Cash flow Cash flow problems can be problems can be calculated using calculated using equations or are equations or are tabulated for fast tabulated for fast problem solvingproblem solving

ExampleExample If you put $1,000 into a savings account If you put $1,000 into a savings account

and the annual interest rate on the and the annual interest rate on the account was 6%, how much money account was 6%, how much money would be in the account after 5 years?would be in the account after 5 years?

The equation to convert a present The equation to convert a present value to a future value is value to a future value is

niPF )1(


(1 + i)(1 + i)nn is called the single payment is called the single payment compound amount factor, and is tabulated for compound amount factor, and is tabulated for various combinations of i (interest rate) and n various combinations of i (interest rate) and n (time period)(time period)

The notation (symbol) for the single payment The notation (symbol) for the single payment compound factor is (F/P, i%, n)compound factor is (F/P, i%, n)

This notation indicates that F (future $ This notation indicates that F (future $ amount) is unknown, that you have P (the amount) is unknown, that you have P (the present value), and given the interest rate (i) present value), and given the interest rate (i) in percent and the time period (n), you can in percent and the time period (n), you can find F.find F.


Back to our example: If you put Back to our example: If you put $1000 into a savings account and $1000 into a savings account and the annual interest rate on the the annual interest rate on the account was 6%, how much money account was 6%, how much money would be in the account after 5 would be in the account after 5 years?years?

Solve by equation: F = 1000(1 + Solve by equation: F = 1000(1 + 0.06)0.06)5 5 = $1338.23= $1338.23

Solve by interest tableSolve by interest table


Example solve by interest table:Example solve by interest table: Go to F/P column with n = 5, for table Go to F/P column with n = 5, for table

with i = 6%: Factor = 1.3382with i = 6%: Factor = 1.3382

F = ($1000) 1.3382 = $1338.2F = ($1000) 1.3382 = $1338.2

n) i%, (F/P,PF

n) i%, (F/P,PF


Biggest thing to keep in mind: make Biggest thing to keep in mind: make sure that your UNITS match; sure that your UNITS match; interest rate, n, and dollar amounts interest rate, n, and dollar amounts may be given on a different basismay be given on a different basis

You try: How much should you put You try: How much should you put into a 10% effective annual rate into a 10% effective annual rate savings account in order to have savings account in order to have $10,000 in four years? (10% interest $10,000 in four years? (10% interest table included on next page)table included on next page)


You are given a future amount of money You are given a future amount of money (F) and ask to solve for a present amount (F) and ask to solve for a present amount of moneyof money

Solve using the i = 10% interest table, Solve using the i = 10% interest table, with n = 4 years; (P/F, 10%, 4) = 0.6830with n = 4 years; (P/F, 10%, 4) = 0.6830

P = F (P/F, 10%, 4) = $10,000*0.6830 = P = F (P/F, 10%, 4) = $10,000*0.6830 = $6,830$6,830

Notice that n is given in years and i is Notice that n is given in years and i is given as an annual interest rate (per given as an annual interest rate (per year); units matchyear); units match


Maintenance costs for a machine are Maintenance costs for a machine are $250/year. What is the present $250/year. What is the present worth of these maintenance costs worth of these maintenance costs over a 12 year period if the annual over a 12 year period if the annual interest rate is 10%?interest rate is 10%? Given:Given: Find:Find:


You have A, you need P: Go to i = You have A, you need P: Go to i = 10% interest chart and go to the P/A 10% interest chart and go to the P/A column (remember in this notation column (remember in this notation your unknown comes first): (P/A, your unknown comes first): (P/A, 10%, 12) = 6.813710%, 12) = 6.8137

P = A (P/A) = -250*6.8137 = -$1703 P = A (P/A) = -250*6.8137 = -$1703 (negative sign indicates a cash sink (negative sign indicates a cash sink or loss of $)or loss of $)

More complicatedMore complicated Question 104, webinar questions on general Ag Eng Question 104, webinar questions on general Ag Eng

principlesprinciples As manager of a large fleet of farm equipment, you are

contracting with an outside mechanics shop to have all complete engine overhauls for tractors, combines, and harvesters at the rate of $7,200 per engine. You have determined the investment needed to construct a new building and equip it to overhaul the equipment yourself would be $180,000. The estimated annual cost for taxes and insurance for the facilities and equipment is 1.25% of the purchase price. The operating cost to perform engine overhauls at a facility that you own would be $5,500 per engine. The equipment and facilities are assumed to have a life of 12 years with a salvage value of $35,000. Interest rate is 7% per year. The minimum number of engines to be overhauled per year to make the investment in equipment and facilities economically feasible is:

NOTE: use 7% interest table (extra handout)NOTE: use 7% interest table (extra handout)

SolutionSolution Approach:Approach:

You are comparing two alternatives, outsourcing You are comparing two alternatives, outsourcing vs. doing it yourselfvs. doing it yourself

Outsourcing: $7200 per engineOutsourcing: $7200 per engine ““in-sourcing”: $5500 per engine, plus facilities, in-sourcing”: $5500 per engine, plus facilities,

equipment, taxes, and insurance (and minus salvage equipment, taxes, and insurance (and minus salvage value)value)

You have to compare these two alternatives using You have to compare these two alternatives using the same basisthe same basis

Choose AChoose A Identify which type of cash flow you have in each situationIdentify which type of cash flow you have in each situation Set the outsourcing term = in-sourcing termSet the outsourcing term = in-sourcing term Solve for x, where x is the number of engines needed to Solve for x, where x is the number of engines needed to

break evenbreak even

SolutionSolution Outsourcing: $7200/engine * x engines, or Outsourcing: $7200/engine * x engines, or

$7200x$7200x ““In-sourcing:”In-sourcing:”

$5500/engine * x engines, or $5500x$5500/engine * x engines, or $5500x New building and equipment = $180,000 (P)New building and equipment = $180,000 (P)

Convert to AConvert to A Interest = 1.25% of building/equipment per year (A)Interest = 1.25% of building/equipment per year (A)

0.0125*180,000 = $22500.0125*180,000 = $2250 Salvage value = $35,000 12 years from now (F)Salvage value = $35,000 12 years from now (F)

Convert to AConvert to A

Use equations (as in solution online) OR Use equations (as in solution online) OR (EASIER): use interest tables!(EASIER): use interest tables!

SolutionSolution

Take home pointsTake home points

If your brain feels like it’s leaking out If your brain feels like it’s leaking out of your ears right now, don’t worry, of your ears right now, don’t worry, it’s normal it’s normal

Best things I did for the PE: Best things I did for the PE: Had a reference book with a great indexHad a reference book with a great index Had a list of where to find critical Had a list of where to find critical

equations and important informationequations and important information Time management tips Time management tips GOOD LUCK!!GOOD LUCK!!

Ag engineering PE review: Exam prep, I-C economics and statistics

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