Question

Athletes performing in bright sunlight often smear black eye grease under their eyes to reduce glare. Does eye grease work? In one study, student subjects took a test of sensitivity to contrast after three hours facing into bright sun, both with and without eye grease. This is a matched pairs design. Provided are the differences in sensitivity, with eye grease minus without eye grease:

		$-0.12$	$-0.05$	$-0.18$		$-0.16$
				$-0.11$

b) Suppose that the subjects are an SRS of all young people with normal vision, that contrast differences follow a Normal distribution in this population, and that the standard deviation of differences is

σ=0.22

.

SOLVE: What is the value of the test statistic? (Enter your answer rounded to two decimal places.)

z=

Use Table A and find the

P

‑value of the test. (Enter your answer rounded to three decimal places.)

P‑value =

Answer 1

Solution:

First, we need to find the mean of the given differences.

Therefore, the value of the test statistic is:

The p-value is:

The p-value is found using the standard normal table.