Twelve monkeys are randomly assigned to two groups. Group 1 gets a preparation of a placebo Monkey tonic and Group 2 gets a course in Applied Monkey Training (AMT, patent pending). Each Monkey's Intelligence Quotient (MIQ) is recorded at the beginning of the study (BASELINE) and after 12 weeks of "treatment" (WEEK12). Data are:
REC GROUP BASELINE WEEK12
--- ---------- ---------- ------
1 1 100 104
2 1 88 93
3 1 106 109
4 1 116 117
5 1 102 104
6 1 106 106
7 2 114 113
8 2 106 108
9 2 100 102
10 2 92 100
11 2 112 110
12 2 92 95
(1) Study design: Consider the design of the study. Is it experimental or observational? Are measurements paired or independent? Lay out a plan for analysis.
(2) Data entry: Create a file with these data. Document the data with a data definition (DD) table.
(3) Compare groups at baseline: Calculate summary statistics (mean, SD, n) for the two groups at baseline. Estimate the mean difference with 95% confidence. Interpret this confidence interval.
(4) Quantify the change within group 1. Let us consider the change in values in group 1. Select the first group for analysis by using the command SELECT GROUP = 1. (You may also use the SELECT Dialogue Box for this purpose. Alternatively, you may create a new data table that includes only Group 1.) Then, do a paired comparison of the WEEK12 and BASELINE measures within this group. Use selected methods from the CONT-PAIR chapter.
(5) Quantify the change within group 2. Release the prior selection (click Cancel Select | OK), and then SELECT Group 2 for analysis. Do a paired comparison.
(6) Compare the change in M IC between the groups: Cancel the previous selection. Then compare the changes in MIQ scores in the two groups (MEANS DELTA GROUP). Do a complete analysis.