Your Name __________________________________ 


Psychology 201W, Spring 2002 

Dr. John A. Johnson

Lab assignment #10  Conducting ttests (Due Friday, April
19)
This lab is worth 30 points.
1. Choose two groups of subjects from our survey data (e.g., male vs.
female, traditional vs. nontraditional age, etc.). If you want to group
according to age, you will have to choose a graduation date cutoff and
divide the full sample at that point. If you want to group according to
those who respond positively versus negatively to a question, you'll want
to divide the sample into those responding above 3 versus below 3. Sort
the data with the Data...Sort... commands in Microsoft Excel along the
grouping variable you have chosen. This will allow you to physically separate
your two groups.
The grouping variable I have chosen is: ____________________________________________
2. Choose a variable on which you think your two groups may differ. Explain
why you think the groups will differ.
3. Using the spreadsheet functions in Microsoft Excel, compute the means
and sums of squares for the two groups you have chosen. Email your spreadsheet
showing these calculations as an attachment to me at j5j@psu.edu
.Report your findings here:
Mean for group one: _______ SS for group one: __________
Mean for group two: _______ SS for group two: __________
4. Compute either in a spreadsheet cell or with a calculator the pooled
standard deviation and the tvalue for your variable. Write out
the formula you used here:
pooled standard deviation: _____________
t value: _______________ degrees of freedom _________
5. Compare your computed t with the critical value of t in
Appendix A2 in the book for a onetailed alpha of .05. Report that tabled
value here and explain whether your computed value of t leads you
to conclude that the groups differ or not.