Lesson 10in SPSS

1. Lesson 10in SPSS How to conduct a One-Way ANOVA With Related Samples

2. The Dataset • Let’s use our example dataset from Lesson 6. • In this dataset, we have four columns—student’s name, their 3rd grade score, 4th grade score, and 5th grade score. • Notice how the data must be set up differently from the independent samples arrangement. • Also, student has been set up as a string (rather than a numeric) variable, but you could assign each student an ID number.

3. Selecting the Analysis • From the SPSS menu bar, choose • Analyze • General Linear Model • Repeated Measures • Note, this may not be available on the student version!

4. Select the Variables • Assign a name to the repeated measurements. Here, I’ve called them gradeperiod. • The computer will give it a name of Factor1. Replace this with what you want. • Type in the number of levels (treatment groups). Next, click on Add

5. Defining the Factor • Our repeated measures factor consists of the measurements for the three different grades. • Click on the variable called thirdperiod from the variables box, then on the right arrow. • Click on the variable called fourthperiod, then on the right arrow. • Finally, click variable called fifth period, then on the right arrow.

6. Then • When all of the repeated measurement treatment groups appear in the Within-Subjects Variable window, Options. • If we had a second variable that was not a repeated measurements, we could put it into the Between-Subjects Factor box. We have no other variables to include, so we’ll continue.

7. Choosing Post Hoc Tests • To get a Post hoc test, we first select our repeated factor (gradeperiod) and move it into the Display Means box. • Next, we check the Compare main effects box. • Then choose a post hoc test. We’ll choose the LSD test (similar to Tukey’s). • We can ask for many other options, but for now, let’s just click on Continue.

8. Ready, Set,… • Now we click on OK.

9. The Output The output looks a little different from when we calculate it by hand. But I’ve highlighted the parts that match our hand calculations. • Notice that we want to use the Sphericity Assumed lines (don’t worry about that now). • And we have two Mean Squares—gradeperiod which equals 20 (the same as when we did it by hand) and Error which is 1.667 (again, the same as when we did it by hand). • We have one F-value, which equals 12 (same as by hand). This is significant, as shown by the sig. of .004, which is less than .05

10. The Output • This box shows our post hoc test results. We find that the first and third grade periods (3rd and 5th) are significantly different. • What’s a little different here because we used the LSD and not the HSD test, it found that the second and third grade periods (4th and 5th) are significantly different, but not the 3rd and 4th. Hmmm, how peculiar!! The reason is that the LSD uses different standard error measurements for each comparison.