In Exercise 3, you worked with summary data from a study conducted by Willoughby, Porter, Belsito, and Yearsley (1999). Here€™s more summary information from that study for students in the imagery condition. The mean memory test performance of the 15 fourth graders was 5.80, with SS equal to 146.06. The mean memory test performance of the 15 sixth graders was 10.47, with SS equal to 305.32. Follow the steps given below to construct a 95% confidence interval around the obtained difference. Designate the fourth graders as group 1 and the sixth graders as group 2.

1. Calculate the degrees of freedom.
2. Use Table B in Appendix C of your textbook to identify the critical t value for a two-tailed test with alpha equal to .05.

3. Calculate the pooled variance estimate.
4. Calculate the estimated standard error.
5. Calculate the 95% confidence interval.
6. Provide a verbal interpretation of the confidence interval.

Table B CRITICAL VALUES OF t -larit orit forit Two-tailed or Nondirectional Test LEVEL OF SIGNIFICANCE One-tailed or Directional Test LEVEL OF SIGNIFICANCE p>.05 p