P554 Statistics in Psych, Prof. Kruschke
P554 Statistics in Psychology,
Prof. Kruschke
Homework for Ch. 3 (Part II). Due at beginning of class, Tu 23 Jan 2007.
General instructions. Please write your full name
at the top of every page you hand in. Please collate and staple
your pages together. Please write clearly and thoroughly explain all
your computations; an unannotated series of formulas that mysteriously
ends up with the correct number will not be given full credit. When
doing the homework, you are encouraged to use all resources at your
disposal to the extent that they help you learn the material;
nevertheless, you must write your own answers in your own words.
- (6 pts.) p. 128, #12.
ALSO characterize the effect size by computing fadj.
- (6 pts.) p. 128, #14.
BUT do it for a desired power of .9, not for .8.
- (8 pts.) Regarding #10, p. 127. Consider the
difference in cortical weights, that is, the difference
Experimental-Control for the matched littermates. (You can use SPSS to
determine the difference; use Transform -> Compute.) There are 12
such differences in each of the three Experiment groups. The three
Experiment groups were run at different times of year.
Suppose we believe that the time of year does
have an effect, however small, on the difference in cortical
weights. We want to run an experiment that has high probability of
detecting the effect of time of year; that is, we want to reject the
null hypothesis that time of year has no effect on the difference in
weights. Use the data from #10 (p. 127) to determine the sample size
we need for a power of .9.
Suppose you are reviewing a grant application. The
investigator describes an intriguing and insightful theory that
predicts there should be an effect of time of year on the difference
in cortical weights. The investigator includes the #10, p.127 data in
his proposal, citing them as pilot data which show a small but
promising hint of an effect. Would you recommend funding the proposal?
Why or why not?