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

1. 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@lsu.edu

2. Overview • “Use of your PE reference books” exercise • Economic analysis and statistics (we’ll do hypothesis testing Thursday) • Throughout: • You will be doing PE style problems (have your references and calculators ready!) • Ask questions

3. Part 1: Exam preparation • References (must have) • Time (in preparing for exam and during exam) • Strategies (preparation and test taking)

4. 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

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

6. 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)

7. 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

8. 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 don’t 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 • Don’t spend time on what you KNOW you won’t touch (there is something you won’t) • The week before the test, do a sample test using the 8 hr exam format (road test caffeine issues, etc.)

9. 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 there’s time, go back and check your answers; also go to the ones that are bugging you (if there are any)

10. 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 doesn’t specify which section is which, but you’ll 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)

11. 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 P&M, irrigation, and structures/environment expert problems)

12. “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.)

13. Question 1 • What is the heat of combustion of propane? • NOTE: heat of combustion is also referred to as heating value

14. Heat of combustion

15. Question 2 • The Atterburg limit test measures what?

16. Question 3 • What is the Young’s modulus of elasticity of stainless steel?

17. Question 4 • What is the density of air at 10° C?

18. Question 5 • What is the curve number for contoured row crops in good hydrologic condition for hydrologic soil group B?

19. 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?

20. Question 7 • What is the typical concentration of suspended solids (SS) in septage?

21. Question 8 • What is the equilibrium moisture content of rough rice at 30° C and 80% RH?

22. Question 8

23. 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

24. 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

25. 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

26. 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

27. 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

28. Reading the z-chart

29. 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?

30. Solution

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

32. Solution

33. You try this one: • 90% of college students have heights greater than what value?

34. Solution

35. 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 (n>30) • Use t chart for small samples • Your statistical equations change a little to reflect the fact that you have a sample

36. 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.

37. Solution

38. 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

39. 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 you’re 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)

40. Engineering econ • Almost all engineering econ problems will involve cashflows; 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

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

42. 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

43. 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.

44. 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

45. Engineering econ

46. 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

47. 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)

48. Engineering econ

49. 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) = $10,000*0.6830 = $6,830 • Notice that n is given in years and i is given as an annual interest rate (per year); units match

50. 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: