STA442/1008 Assignment 2

Quiz on Friday Sept. 30th

This assignment is really just an opportunity to get your feet wet with unix and SAS. It is based on Chapter 2 and associated lecture material, so please begin by reading Chapter Two of the online text.

In a study comparing the effects of two soporific drugs, 10 subjects were randomly assigned to receive Drug 1, and 20 were randomly assigned to receive Drug 2. Hours of sleep were recorded the night before taking the drug, and then again the night the drug was administered. The variable "Extra" is the difference (measurement at time 2 minus measurement at time 1). Here are the data.

   extra  drug
1    0.7     1
2   -1.6     1
3   -0.2     1
4   -1.2     1
5   -0.1     1
6    3.4     1
7    3.7     1
8    0.8     1
9    0.0     1
10   2.0     1
11   1.9     2
12   0.8     2
13   1.1     2
14   0.1     2
15  -0.1     2
16   4.4     2
17   5.5     2
18   1.6     2
19   4.6     2
20   3.4     2

Using SAS, find out if there is a significant difference in the effectiveness of the two drugs, at the usual 0.05 level. In addition to a simple "Yes" or "No," you must be able to express the results of your analysis in simple, non-technical language. What did you find?

Do this assignment preparation for Quiz 2. Please bring your complete, unedited log file and list file to the quiz. You may or may not be asked to hand them in. Please be very careful to ensure that the log and list file are from the same SAS run. It makes a big difference, and we can usually tell. Also, sometimes students are loose about the difference between the log file and a simple printout of the program (command) file. To be safe, do not bring a copy of the program file to the quiz.

Do not write anything on your printouts prior to Quiz 2 except maybe your name and student number.

In addition to a statement of what you conclude from the data, think about the following:

1. Does it make sense to describe the variable "extra" as increase in sleep time? Answer Yes or No.
2. What is the independent variable? What is the dependent variable?
3. Is this an observational study, or experimental?
4. Does this study establish that type of soporific drug caused an average difference in the variable Increase in Sleep Time?
5. Of course you should be able to give the mean and standard deviation of Increase in Sleep Time for subects receiving Drug 2, say what's the value of the test statistic, what's the p-value, are the results statistically significant, and so on.

These data come from a paper published a long time ago: