Assignment 7 (SAS Asst 1) Comments on Answers
- Pregnancy Question: This is a clearly paired data problem so
that the unpaired test is not valid. You use the data step to create
a variable equal to the difference between the two pregnancy glucose
levels. Then proc means provides means, SDs, standard errors and a
t-test for the hypothesis that there is no difference in mean glucose
levels. The P-value is just a bit below 0.05 (2 sided) so the conclusion
is that there is a significant difference. The evidence is not too strong,
however. The probability plots are satisfactory.
- This is a two sample problem. The null hypotheses of equal means and
of equal variances are both accepted. The normal probability plots (you
get two if you specify by sex in proc univariate) show
no problem for either sex.
- The two sample t-test rejects the hypothesis of equal means
whether you assume the variances are equal or not. The assumption
of equal variances is accepted by any test and the normal probability
plots are OK.
Mon Mar 9 17:28:22 PST 1998