P554 Statistics in Psych, Prof. Kruschke
P554 Statistics in Psychology,
Prof. Kruschke
Homework for Ch. 6. Due at 9:30am, Tu 1 May 2007.
General instructions. Please write your name and student
ID 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.
Turn this in at the Psych Main Office by 9:30am Tuesday May 1. It
should go to Stephen Denton.
1 (7 pts.)
Use data from #11, p. 272.
Do a simple linear regression of the DV on dosage. Do this in
SPSS. Report the statistical test, including df values, and conclusion.
Do a Oneway ANOVA with polynomial contrasts (in SPSS). Report the
results for the linear trend, including df values, and conclusion
regarding the linear trend.
What is different about the two tests in the previous two parts?
Describe in terms of the models being compared.
2 (7 pts.)
Use data from #11, p. 272.
In SPSS, type in three dummy coded regressors, corresponding to
the linear, quadratic and cubic trends. Do a multiple regression on
the three regressors. Include a table that shows the data and the
dummy codes, and include a summary of the significance test on each
regressor. Finally, point out how these results correspond to the
Oneway ANOVA polynomial contrasts that you did in the previous
exercise.
3 (6 pts.)
Use data from #14, p. 273.
In SPSS, do a Oneway ANOVA with polynomial trend analysis. (This
is book part a.)
Now do book part f; i.e., transform the data and re-do the
analysis. Do any conclusions change?
Which analysis (original data or tranformed data) is more
appropriate? Why?