Independent Samples t-test

After studying the effects of age on memory, three researchers decide that most age effects on memory can be reduced to very specific types of information that we're more likely to forget as we get older.They then designed a new memory test that focused specifically on the types of information they believed were more likely to be forgotten by older adults. They administered this test to two groups of adults. Group 1 consisted of men and women between the ages of 41 and 60 and Group 2 consisted of men and women between the ages of 68 and 80. Test scores are listed below. Test the hypothesis, of any age difference in memory for this information. Use a significance level of .05.

Group 1 Group 2

7 5

3 4

3 4

2 5

3 5

8 7

8 8

5 8

8 9

5 8

5 3

4 2

6 5

10 4

10 4

5 6

1 7

1 7

4 5

3 6

5 4

7 3

1 2

9 7

2 6

5 2

2 8

12 9

15 7

4 6

1. Create a new SPSS data file. Define the necessary variables. Think of each score as belonging to a single participant and assign an ID # for each participant (this should be your first variable). Don't forget to include a variable for group (younger vs older) so that you can complete the comparison of means test.

2. Input the data shown above.

3. Run a non-directional (i.e., 2-tailed) t-test for independent samples on the data above, requesting the calculation of descriptive sample statistics. Record the results below.

Mean (X) __________ Mean (Y) __________

Median (X) __________ Median (Y) __________

Std Dev (X) __________ Std Dev (Y) __________

Standard Error (of the Difference Between Means) __________________

Mean Difference _____________________

Calculated t _________________ p-value ____________

4. Is this result statistically significant? Yes No

5. What are the null & alternative hypotheses for this test? Write them out in symbolic form.

_______________________________________

_______________________________________

6. Would you retain or reject your null hypothesis with this result? ____________

7. Are the researchers correct with regard to their hypothesis that older adults are more likely to forget this particular type of information? Why or why not?