Psych 341, Spring, 1998
Lab Exercise-Mult. Comparisons
The following is mainly a paper and pencil exercise. I do not expect you to do this in
lab, because you will need to use your text and a calculator. Just hand this in next week.
[I assigned this along with the trend analysis lab.]
Solomon, Secker-Walker, Skelly, and Flynn (1996) in the Journal of Behavioral Medicine studied smoking behavior in pregnant women. They looked at the women's determination to quit smoking while pregnant. They interviewed 349 women at their first pre-natal visit, all of whom were smokers when they became pregnant, and classified them into four groups.
Label | Condition | Description |
PC | Precontemplation | Smokes and has no plan to quit smoking |
C | Contemplation | Smokes but is thinking of quitting |
P | Preparation | Smokes, but has made some effort at quitting |
A | Action | Has already quit |
They wanted to look at the subsequent smoking behavior of these subjects over the
course of their pregrancy, but one important consideration is how much these women smoked
when they became pregrant. If the groups differ on that variable, that might affect the
interpretation of the results.
The means and standard deviations of these four groups, in terms of cigarettes/day when they became pregnant, are given below. What can we conclude about group differences in pre-pregnant smoking behavior?
PC |
C |
P |
A |
|
Mean |
24.8 |
16.6 |
28.8 |
13.7 |
St. Dev. |
13.3 |
5.2 |
12.2 |
8.8 |
nj |
69 |
37 |
153 |
90 |
Notice that this is not really a simple problem. Your sample sizes are grossly unequal,
and you have problems with heterogeneity of variance. Not to worry, I tell you how to deal
with this in the text. The only difference is that the text talks about it as part of the
Newman-Keuls, whereas I have asked you to run a Tukey test. You should be able to figure
that transition out yourself.
Notice that this is a real data set, and this is the kind of problem that each of you can expect to face in the future. This isn't some trumped up example that doesn't apply to anything important. What can you conclude from these data?
dch
1/21/97
Last revised: 3/6/2009