1. Rouse@iastate.eduApplying science to fuel and feed our global society Jim Rouse SCC-33 / UCTA 1/27/2010 Alpha dogs: The significance of the LSD Rouse@iastate.edu 515-294-5604

2. Rouse@iastate.eduApplying science to fuel and feed our global society Today’s topics Alpha levels—survey results Perceptions of alpha Impact on LSD Costs of decision errors

3. Rouse@iastate.eduApplying science to fuel and feed our global society Survey: What level do you use? n=27 (21 Public, 6 industry)

4. Rouse@iastate.eduApplying science to fuel and feed our global society Survey comments Software provides LSD at 0.05 and 0.2. … often calculate my own at 0.1, because …0.05 is too inclusive …0.2 is too exclusive. We use 0.1, but will use 0.05 if we really want to select hard. Which one is accurate?

5. Rouse@iastate.eduApplying science to fuel and feed our global society Impact on LSD Increase in alpha will decrease LSD 0.05 is indeed more inclusive

6. Rouse@iastate.eduApplying science to fuel and feed our global society Least significant difference

7. Rouse@iastate.eduApplying science to fuel and feed our global society Making Decisions H 0  No differences H A  Differences H 0 is trueH 0 is false Accept H 0 CorrectType II error Reject H 0 Type I errorCorrect / T-III

8. Rouse@iastate.eduApplying science to fuel and feed our global society Making Decisions Type I error rate = α, typically 0.05 Type II error rate = β, typically unspecified and unknown

9. Rouse@iastate.eduApplying science to fuel and feed our global society Making Decisions α is inversely related to β Lower prob of Type I error = higher prob of Type II error Key: What is appropriate balance? Based on cost of errors

10. Rouse@iastate.eduApplying science to fuel and feed our global society What is the cost of Type I error? –2 hybrids are “same”, but we think not Result: Choose one over another –No difference, no cost Grower’s perspective only! Decision Errors

11. Rouse@iastate.eduApplying science to fuel and feed our global society What is the cost of Type II error? –2 hybrids are “different”, but we think not Result: Choose either –Choose the better one, no cost –Choose the worse one, cost –Half the time, T-II errors cost growers Loss depends on true difference –Yield difference between choices Decision Errors

12. Rouse@iastate.eduApplying science to fuel and feed our global society Finding Value in the Data Determine relative cost of errors Adjust α to minimize losses –(a la Carmer in Crop Science, 1976) Difference between reality and theory? –Many growers use α = 1 –Eliminates Type II errors

13. Rouse@iastate.eduApplying science to fuel and feed our global society That’s all! Questions—Comments—Discussion

14. Rouse@iastate.eduApplying science to fuel and feed our global society New truths… “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” —Max Planck (founder of quantum theory)

15. Rouse@iastate.eduApplying science to fuel and feed our global society Background “I have great faith in fools; self-confidence my friends call it.” —Edgar Allan Poe “Don’t math it all up.” —Glenda Rouse, my wife