STA305s14 Computer Assignment Four
Quiz in lecture on Monday March 3d

The data set from the scab disease study (first introduced in Assignment 2) was incomplete. Actually, the treatment was applied to fields in either the Spring or the Fall. You have been analyzing just the control and Fall data. The full data set is given in the file ScabDisease.data. First, produce a table of means, standard deviations and sample sizes for the 7 experimental conditions. Then carry out tests to answer the questions below. For each test, be able to

• State the null hypothesis in terms of μ values. All tests will be non-directional.
• Give the value of the F statistic. The answer is a number from your printout.
• Give the p-value. The answer is a number from your printout.
• Do you reject H₀ at α=0.05?
• In plain, non-statistical language, what do you conclude from the test? Remember, even though the alternative hypotheses are non-directional, you will state directional conclusions when you can.

1. First, test whether expected amount of scab disease for each treatment is different from the expected amount of scab disease in the control condition. That's six tests.
2. Is the average (mean) expected amount of scab disease in the 3 Fall conditions different from the expected amount of scab disease in the control condition?
3. Is the average (mean) expected amount of scab disease in the 3 Spring conditions different from the expected amount of scab disease in the control condition?
4. Is the average (mean) expected amount of scab disease in the 3 Spring conditions different from the average (mean) expected amount of scab disease in the 3 Fall conditions?
5. For each amount of sulphur, is the expected amount of scab disease different depending on whether the treatment is applied in Fall or the Spring? That's three tests.

Bring both your log file and your procedure output file to the quiz. You will be asked to hand them in with your quiz. Please put your name and student number in the title statement.

Please be reminded of the rules for computer assignments and quizzes. See the syllabus for more detail.

• You may copy freely from me, but do not look at anyone else's SAS code before the quiz.
• Do not show your SAS code to any other student in the class.
• Do not write anything on the printouts.
• Important: Comment statements and other typed material that would help with interpretation of the computer output are expressly forbidden. For example, you may not type assignment questions or answers into your code, or otherwise cause them to appear on your log file or procedure output file. Any such material is an unauthorized aid for the purposes of this course, and if you use or possess an unauthorized aid, you will be charged with an academic offence.
• The log and procedure output files must be generated at the same time by the same SAS program or you may lose a lot of marks.

The data used in this assignment come from an R dataset called chickwts. The assignment is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License. Use any part of it almost any way you like, as long as you share the results freely. See the license for details.