Your Name __________________________________ Psychology 201W, Spring 2002 Dr. John A. Johnson

Lab assignment #10 -- Conducting t-tests (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 t-value 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 A-2 in the book for a one-tailed 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.