# Thread: Confidence Interval Using Calculator

1. ## Confidence Interval Using Calculator

A coach uses a new technique in training middle distance runners. The times for 9 different athletes to run 800 meters before and after this training are shown below.
Assume that the conditions and assumptions for inference are satisfied.

Athlete: A B C D E F G H I
Time Before: 115.2 120.9 106.0 112.4 107.5 119.1 121.3 110.8 122.3
Time After: 116.0 119.1 105.1 111.9 109.1 115.2 118.5 110.7 120.9

a) Do the data suggest that there is a significant difference between the "before" and "after" times? Perform the appropriate test at the significance level 1%. Clearly state your conclusions.

I'm not sure what test to use would this be a 2-propZtest? or 2-sampTtest?

b) Construct a 99% confidence interval for the mean difference between the "before" and "after" times.

2. You would run a 2-Sample T-Test. On your TI-83, input the values for the Before/After into a list. Do you know how to do that:

STAT>>EDIT, and then input Before in L1, and after in L2.

You then run your 2-Sample T-Test with population mean for L1 greater than population mean for L2, as you are trying to demonstrate that the times for these runners after their training is LESS THAN the times for the runner before their training.