1. I OWA S TATE U NIVERSITY Department of Animal Science Swine Statistics Ken Stalder Iowa State University

2. I OWA S TATE U NIVERSITY Department of Animal Science Why are we teaching statistics in a swine systems course? n Today’s pork operations are more sophisticated. n Operations involve a series of tasks l Breeding & Conception Rates AI Technicians Service Sires Day effects l Farrowing rate Fallout by day of gestation Breeding issues Health l Farrowing Production Number born alive Stillbirth rate Number weaned

3. I OWA S TATE U NIVERSITY Department of Animal Science Why are we teaching statistics in a swine systems course? n Today’s pork operations are more sophisticated. n Operations involve a series of tasks l Variation about these number can be just as important when evaluating production information Conception rates day to day within a week week to week within a month month to month within a quarter month to month within a season month to month within a year season within a year year to year within a herd herd to herd within a production system production system within a country Country within the world

4. I OWA S TATE U NIVERSITY Department of Animal Science Example of this type of information

5. I OWA S TATE U NIVERSITY Department of Animal Science Statistics meaning – dictionary.com 1. ( used with a singular verb ) the science that deals with the collection, classification, analysis, and interpretation of numerical facts or data, and that, by use of mathematical theories of probability, imposes order and regularity on aggregates of more or less disparate elements. 2. ( used with a plural verb ) the numerical facts or data themselves.

6. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Mean Treatment 1 Treatment 2 Treatment 3 270290 300250340 280 330 280290300 270280300Total 1400139015604350 n55515 280278312290 Example from Kaps and Lamberson, Biostatistics for Animal Science, 2004

7. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u What does the mean really tell us? u Depends what the question is? n Evaluating titer levels for some disease n Determining whether a production value is within some normal level n Temperature values l Most equipment does not hold values like temperature at a mean but within some normal operating levels n Other examples

8. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u After obtaining your data you can start to ask yourself more complex questions u May seem simple but can be very descriptive n Range Simply the high and low values

9. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Interpreting the meaning of the range u Depends on data being examined n Within a production system n Within an operation n Within a group of pigs l Grow – Finish pigs Using Paylean™ l Nursery age pigs l Piglets in farrowing l Feeding animals

10. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Mean Treatment 1 Treatment 2 Treatment 3 270290 300250340 280 330 280290300 270280300Total 1400139015604350 n55515 280278312290 Range270-300250-290290-340270-340 Example from Kaps and Lamberson, Biostatistics for Animal Science, 2004

11. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u After obtaining your data you can start to ask yourself more complex questions u May seem simple but can be very descriptive n Median n What is the median? l It is the middle number where ½ the values are above and ½ the values are below l Often good to understand along with the mean

12. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u How do you calculate the median? n Line up all of the values l If you have an odd number of values it is the number with the same number of observations on either side 5, 7, 13, 25, 99 Median = 13 l If you have an even number of values it is the average of the two middle numbers that have the same number of observations on either side 5, 7, 13, 15, 25, 99 Median = (13 + 15) / 2 = 14

13. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u What does the median tell us? n It is one measure of the variability? l Less precise than others l If the data are “close” normally distributed then the mean and median values will be similar Example 5, 7, 13, 25, 99 Median = 13 Mean = 29.8 l Often used in when evaluating financial information Net income from contract growers

14. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Mean Treatment 1 Treatment 2 Treatment 3 270290 300250340 280 330 280290300 270280300Total 1400139015604350 n55515 280278312290 Median280 300290 Example from Kaps and Lamberson, Biostatistics for Animal Science, 2004

15. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u After obtaining your data you can start to ask yourself more complex questions u May seem simple but can be very descriptive n Mode n What is the mode? l It is the value that occurs most frequently l Similar to the median it is good to understand along with the mean

16. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Mean Treatment 1 Treatment 2 Treatment 3 270290 300250340 280 330 280290300 270280300Total 1400139015604350 n55515 280278312290 Mode270 & 280280 & 290300280 Example from Kaps and Lamberson, Biostatistics for Animal Science, 2004

17. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u After obtaining your data you can start to ask yourself more complex questions u May seem simple but can be very descriptive u Often see data presented in n Quartiles – divide up the data into 4 equal portions l Calculate means of the top 25% and bottom 25% of producers n Percentiles – divide up the data into 10 equal percentages (10, 20, 30…….., 90, 100) l Calculate means from the top 10% of herds and bottom 10% of herds

18. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u What use do data have if broken up into n Quartiles or Percentiles l Compare to other similar operations within a production system Benchmark against operations within a system Establish production goals Establish a bonus structure l Compare to other operations within a country Really examining how an operation compare to others under similar buying systems, financial circumstances, etc. l Compare to other operations across the world Ultimately defines the most efficient production around the world Generally the economic situation is most important in these comparisons as it will ultimately determine where pork is produced world-wide.

19. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u The mean, mode, median, range are really descriptive statistics. n Often used in a snap shot in time u These values really tell us nothing about the variability with our data. u Why is understanding the variability or the variation in a production system important?

20. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Standard deviation = a measure of the variability within some data u Under the normal distribution assumptions: u 68% of the data will fall within ±1 standard deviation of the mean u 95% of the data will fall within ±2 standard deviations of the mean u Almost all (99.7%) of the data will fall within ±3 standard deviations of the mean

21. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Standard deviation = a measure of the variability within some data Image from: http://www.spcforexcel.com/normal-probability-plots

22. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Standard deviation = a measure of the variability within some data Image from: http://www.spcforexcel.com/normal-probability-plots 68.3 % of the area represented ±1 SD 95.4 % of the area represented ±2 SD 99.7 % of the area represented ±1 SD

23. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Standard deviation = a measure of the variability within some data u The normal curve can take on a variety of shapes depending on the variation that exists within the data

24. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Standard deviation = a measure of the variability within some data u What does the SD really tell us when looking data from swine operations? l Number born alive l Number weaned l Weaning weight l Weaning age l Return to estrus l Backfat l Loin muscle area l Percent lean

25. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Mean Treatment 1 Treatment 2 Treatment 3 270290 300250340 280 330 280290300 270280300Total 1400139015604350 n55515 280278312290 Standard Deviation 11.014.719.422.5 Example from Kaps and Lamberson, Biostatistics for Animal Science, 2004

26. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures commonly used when evaluating swine data u Why is understanding the variability or the variation in a production system important? u It starts by understanding a term called “throughput” n Units produced per unit of fixed costs l Lbs of pork per $ fixed costs a slaughter facility l Lbs of sausage per $ fixed costs in a processing facility l Pigs produced per $ fixed costs in a breed to wean operation n Variation usually takes away from throughput l Looking for variation causes to correct or reduce

27. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures to interpret scientific publications u Graduates going into more technical fields related to swine production u Often asked to interpret information for the company you work for or the clientele you serve u Need be able to understand scientific publications

28. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures to interpret scientific publications u Most papers have a null hypothesis or H 0 n No difference between treatment means u What does P < 0.05 mean n I reject the null hypothesis of no treatment mean difference n I am saying there is a difference n 5% chance of declaring a difference when it really was not there.

29. I OWA S TATE U NIVERSITY Department of Animal Science Basic statistical measures to interpret scientific publications u Most papers have a null hypothesis or H 0 n No difference between treatment means u Does P > 0.05 mean that there is no difference? n Not necessarily n Did the research have enough animals or pens of animals in each treatment to detect a difference n If not best to say no difference was observed n The more variation with the data measured the more animals or pens of animals that have to be tested l Example Reproductive traits – number born alive and weaned Performance traits – growth rate and feed efficiency Carcass traits – backfat, loin muscle area, percent lean

30. I OWA S TATE U NIVERSITY Department of Animal Science Any questions or comments?