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.

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?

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?

Solomon, L. J., Secker-Walker, R. H., Skelly, J. M., & Flynn, B. S. (1996) Stages of change in smoking during pregnancy in low-income women. Journal of Behavioral Medicine, 19, 333-344.

dch
1/21/97

Last revised: 3/6/2009