P554 Statistics in Psych, Prof. Kruschke
P554 Statistics in Psychology,
Prof. Kruschke
Homework for Ch. 13. Due at beginning of class, Tu 17 Apr 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.
- Consider only the data from p. 678, #10 (10 pts.)
For these data, do the following:
* In SPSS, do an omnibus test, using a multivariate
analysis. Include only the multivariate ANOVA table in what you turn
in. Under the table, state the conclusion of the test.
* Suppose we have two planned comparisons. One is the "Circle"
versus the "White" patterns. A second is the average of the "Face",
"Circle" and "Newspaper" versus the "White" pattern. Conduct the two
comparisons in SPSS. Include the relevant output tables. Be sure to
explain exactly what you did to get those results. Also, state the
conclusion of the tests, making sure to use the Bonferroni correction.
* If the tests had been post-hoc instead of planned, what would
the critical value have been? (HINT: See Eqn. 27, p. 652.)
- (10 pts.)
* Suppose we are planning a four-group within-subjects study. For
example, suppose we are planning the research described in Exercise
10, p. 678. We plan to use the multivariate approach to analyze our
data and we will use an alpha level of .05. We want to achieve a power
of .80.
* We believe that the maximum group mean will be about 25, the
minimum group mean will be about 22, and the standard deviation within
groups will be about 4. Suppose we also believe that the minimum
correlation among the four groups will be about .2. What is the
minimum number of subjects we need?
* If we ran the study between-subjects, what is the minimum
total number of subjects we would need?
* Repeat the previous two parts, but this time get the max and min
group means, the SD within groups, and the min correlation among the
four groups, from the data in Exercise 10, p. 678. That is,
use the data as if they were pilot data, from which we were going to
determine the number of subjects for the full experiment. (If these
"toy" data generate values outside the range in the power tables,
explain the process by which the values would be used if they were in
range.)