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

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

• Marybeth Lima, Ph.D., P.E.
• Cliff Nancy Spanier Alumni Professor
• Biological Agricultural Engineering
• E-mail mlima1_at_lsu.edu

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Overview

• Use of your PE reference books exercise
• Economic analysis and statistics (well do
  hypothesis testing Thursday)
• Throughout
• You will be doing PE style problems (have your
  references and calculators ready!)
• Ask questions

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Part 1 Exam preparation

• References (must have)
• Time (in preparing for exam and during exam)
• Strategies (preparation and test taking)

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References

• Are an absolutely critical part of your
  preparation you will not pass the exam without
  the proper references
• There is a comprehensive list of references in
  the booklet entitled A Guide to Professional
  Licensure for Agricultural, Food, and Biological
  Systems Engineers.
• http//www.asabe.org/pei/index.html
• Some references are more useful than others

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References I used for 80 of the exam problems
(must haves)

• A Guide to Professional Licensure for
  Agricultural, Food, and Biological Systems
  Engineers
• The notes from this on-line review course (bound)
• ASAE Standards (I used the 2000 edition for the
  2005 exam and was fine)
• The Civil Engineering Reference Manual for the PE
  exam (soil and water, wastewater, pumps, econ
  tables, INDEX)
• The Mechanical Engineering Reference Manual for
  the PE exam (HVAC, machine systems, econ tables,
  fans, INDEX)
• You dont have to bring both PE manuals but have
  one Id recommend civil over mechanical because
  of broad coverage of topics. If you pick the
  civil manual, bring ASHRAE Fundamentals or
  another strong HVAC book.

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Other references I used

• Wastewater Engineering, Metcalf and Eddy (used
  3rd edition)
• Henderson, Perry and Young, Principles of Process
  Engineering
• Wood Engineering, Gurfinkel (any wood engineering
  book will do you need the tables at the back
  you may find in civil vs. ag parts of library)
• A soil physics book
• MWPS-1 Structures and Environment Handbook (op)
• Schwab et al. Soil and water conservation
  engineering (4th edition)

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References I brought and did not use

• Irrigation Systems
• NRCS handbook parts 650 and 651
• Goering and Hansen, Engine and tractor power
• Shuler and Kargi, Bioprocess Engineering Basic
  Concepts
• Salvendy, Handbook of Human Factors
• MWPS-8, Swine Housing and Equipment Handbook

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Time preparing for the exam

• Get your references and get used to using them
  (tab Standards)
• Make an index of where specific information is
  located so that you dont have to search during
  the exam
• Do and re-do all the problems you are given in
  the on-line course
• Do problems in your reference books (especially A
  Guide to Professional Licensure for ag, food and
  bio engineers)
• Focus your time general ag engineering
  knowledge, your expertise area, your secondary
  knowledge areas
• Dont spend time on what you KNOW you wont touch
  (there is something you wont)
• The week before the test, do a sample test using
  the 8 hr exam format (road test caffeine issues,
  etc.)

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Time during the exam

• The exam is designed such that each question
  takes an average of six minutes
• There are 1 minute problems and 15-20 minute
  problems
• Go through the test and answer questions in the
  following order
• The quick, easy ones that you know you can do
• The ones you know that you can do that take a
  little more time
• Guess (with gusto!) at the ones that are beyond
  your scope
• Guess the same letter every time
• Go back and do the ones that you think you can do
  that are time consuming
• If theres time, go back and check your answers
  also go to the ones that are bugging you (if
  there are any)

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Strategies

• You need to develop problem recognition
• You need to develop flexible thinking
• Pick what you will not answer and guess with
  pleasure (I guessed at 10 of the questions on
  the exam)
• Many times you can eliminate two of the four
  choices easily (even with areas you know nothing
  about)
• The sample exam in the licensure book was very
  much like the actual exam in terms of format and
  somewhat alike in terms of types of problems
• The exam doesnt specify which section is which,
  but youll have four or five consecutive
  questions that are from the same area and then on
  to the next area)
• Knowing fundamental knowledge is critical (the PE
  reference manuals in civil and mechanical were
  invaluable)

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Strategies

• You need to answer 60 of the problems correctly
  to pass
• Having a strong base in general agricultural
  engineering knowledge will take you over the
  top
• My experience for the various expertise areas,
  about 60 of the problems were solvable without
  expert knowledge in the area (as long as you had
  good references and knew where to look for info)
• The other 40 of the expertise questions were
  expert knowledge level, involved problems (I
  skipped PM, irrigation, and structures/environmen
  t expert problems)

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Use of your PE reference books exercise

• On the PE exam, you want the 1 minute questions
  that appear on the test to take 1 minute to
  answer
• These questions are testing your basic knowledge
  of the field and your ability to bring and use
  the proper references
• Practice find the answers to the questions on
  the following slides
• Approach
• First, classify the problem in which area of the
  Ag PE do you think the problem is contained? In
  which references might you find the information?
• When you find the answer, record the value, the
  reference in which you found the answer, AND
  descriptive information within the reference
  (page number, table number, figure number,
  equation number, etc.)

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Question 1

• What is the heat of combustion of propane?
• NOTE heat of combustion is also referred to as
  heating value

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Heat of combustion
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Question 2

• The Atterburg limit test measures what?

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Question 3

• What is the Youngs modulus of elasticity of
  stainless steel?

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Question 4

• What is the density of air at 10 C?

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Question 5

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

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Question 6

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

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Question 7

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

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Question 8

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

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Question 8
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Questions on this exercise?

• In my experience, 10-20 of the questions on the
  exam were of this nature
• Fast if you had the right references and knew
  where to find the information

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1-C Economics and statistics

• A broad area with applications across the board
  (5 of exam questions)
• Statistics is commonly used because you need
  descriptive information to help interpret data
• Economics is commonly used for making engineering
  decisions
• My suggestion for stats and econ use the CE or
  ME PE reference book (Lindeburg)
• Chapter on statistics
• Table at the back (z-chart)
• Get a t-chart as well!!
• Chapter on engineering economic analysis
• Full interest tables at the back

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Statistics basics

• Measures of central tendency
• Mean, median, mode
• Measures of dispersion
• Standard deviation, variance, range, coefficient
  of variance
• For PE have equations to determine measures of
  central tendency and dispersion
• There are slight differences in equations
  depending on if you are working with a population
  or a sample

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Statistics Distributions

• A number of distributions can be used to describe
  various data sets or can be used to solve
  engineering problems in relation to these data
  sets
• Sampling distributions involving means
• Normal (aka Gaussian) our focus
• Student t distribution
• Sampling distributions involving variance
• F distribution
• Chi-Square

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Normal distribution review

• Symmetrical distribution with mean m and standard
  deviation s
• Area under curve represents 100 of possibilities
• 50 to the right of the mean
• 50 to the left of the mean
• A value is higher than the mean for this
  distribution to the right of the mean, lower to
  the left of the mean
• x represents where you are in the distribution z
  is the number of standard deviations away from
  the mean that you are
• z is positive to right of mean
• z is negative to left of mean

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Reading the z-chart
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Typical PE style problems

• The population mean for college students heights
  is 67 inches, and the population standard
  deviation is and 4 inches. These data are
  normally distributed.
• What percentage of college students have heights
  less than 71 inches?

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

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Solution
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You try this one

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

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Solution
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Sampling

• We almost never work with populations
• We take samples and try to draw conclusions about
  a population based on a sample
• Use z chart for large samples (ngt30)
• Use t chart for small samples
• Your statistical equations change a little to
  reflect the fact that you have a sample

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Confidence intervals

• Commonly used in research and process control
• 95 confidence intervals are common
• For example, what is the 95 confidence interval
  of a set of 50 data points the mean of this data
  set is 150 and the standard deviation is 15.

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Solution
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Questions on statistics?

• Tips
• Get a general reference with equations and make
  sure you have a z chart and a t chart
• get z from A, and A from z
• Know confidence intervals
• Look at process control and hypothesis testing

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1-C Engineering economic analysis

• Typically easy questions on the exam if you know
  how to use factor tables (slang, interest tables)
• Tabulated in the ME reference manual, A-132-150
  or CE manual A-112-130
• Types of problems in engineering economic
  analysis
• Decision making you have a material youre
  trying to choose, or a part, or a machine.
  Compare which is most economical given present
  cost, maintenance costs, etc.
• Replacement/retirement analysis (when should you
  replace or retire a product?)
• Rate of return problem (to find percentage return
  on an investment)
• Break even point on an investment
• Loan repayment (how long will it take)
• Economic life analysis (life cycle costs)
• Benefit/cost analysis (do the benefits outweigh
  the costs)

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Engineering econ

• Almost all engineering econ problems will involve
  cash flows it is like a material balance using
  money instead of mass.
• Types of cash flows
• Single payment cash flows (P or F)
• P present value of money
• F future value of money
• Uniform series cash flow (A)
• An amount that is the same every month, like a
  house or car payment
• Gradient series cash flow (not used much) (G)
• A value that goes up or down the same amount
  every time period
• You use types of cash flows to compare
  alternatives and solve econ problems

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Engineering econ

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

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• Example
• If you put 1,000 into a savings account and the
  annual interest rate on the account was 6, how
  much money would be in the account after 5 years?
• The equation to convert a present value to a
  future value is

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Engineering econ

• (1 i)n is called the single payment compound
  amount factor, and is tabulated for various
  combinations of i (interest rate) and n (time
  period)
• The notation (symbol) for the single payment
  compound factor is (F/P, i, n)
• This notation indicates that F (future amount)
  is unknown, that you have P (the present value),
  and given the interest rate (i) in percent and
  the time period (n), you can find F.

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Engineering econ

• Back to our example If you put 1000 into a
  savings account and the annual interest rate on
  the account was 6, how much money would be in
  the account after 5 years?
• Solve by equation F 1000(1 0.06)5
  1338.23
• Solve by interest table

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Engineering econ
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Engineering econ

• Example solve by interest table
• Go to F/P column with n 5, for table with i
  6 Factor 1.3382
• F (1000) 1.3382 1338.2

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Engineering econ

• Biggest thing to keep in mind make sure that
  your UNITS match interest rate, n, and dollar
  amounts may be given on a different basis
• You try How much should you put into a 10
  effective annual rate savings account in order to
  have 10,000 in four years? (10 interest table
  included on next page)

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Engineering econ
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Engineering econ

• You are given a future amount of money (F) and
  ask to solve for a present amount of money
• Solve using the i 10 interest table, with n
  4 years (P/F, 10, 4) 0.6830
• P F (P/F, 10, 4) 10,0000.6830 6,830
• Notice that n is given in years and i is given as
  an annual interest rate (per year) units match

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Engineering econ

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

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Engineering econ

• You have A, you need P Go to i 10 interest
  chart and go to the P/A column (remember in this
  notation your unknown comes first) (P/A, 10,
  12) 6.8137
• P A (P/A) -2506.8137 -1703 (negative sign
  indicates a cash sink or loss of )

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More complicated

• Question 104, webinar questions on general Ag Eng
  principles
• 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)

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Solution

• Approach
• You are comparing two alternatives, outsourcing
  vs. doing it yourself
• Outsourcing 7200 per engine
• in-sourcing 5500 per engine, plus facilities,
  equipment, taxes, and insurance (and minus
  salvage value)
• You have to compare these two alternatives using
  the same basis
• Choose A
• Identify which type of cash flow you have in each
  situation
• Set the outsourcing term in-sourcing term
• Solve for x, where x is the number of engines
  needed to break even

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Solution

• Outsourcing 7200/engine x engines, or 7200x
• In-sourcing
• 5500/engine x engines, or 5500x
• New building and equipment 180,000 (P)
• Convert to A
• Interest 1.25 of building/equipment per year
  (A)
• 0.0125180,000 2250
• Salvage value 35,000 12 years from now (F)
• Convert to A
• Use equations (as in solution online) OR
  (EASIER) use interest tables!

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Solution
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Solution
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Take home points

• If your brain feels like its leaking out of your
  ears right now, dont worry, its normal ?
• Best things I did for the PE
• Had a reference book with a great index
• Had a list of where to find critical equations
  and important information
• Time management tips
• GOOD LUCK!!