Question

A researcher would like to evaluate the effectiveness of a pain-relief patch designed for lower back pain. Prior to testing the patch, each of n = 8 patients rates the current level of back pain on a scale from 1 to 10. After wearing the patch for 90 minutes, a second pain rating is recorded. The data are as follows:

                  Before      After

                        6            2

                        8            3

                        9            4

                        8            1

                      10           2

                        5            3

                        9            8

                        7            7

Compute the mean and variance for the sample of difference scores.

Do the results indicate a significant difference?

Use a two-tailed test with α = .05

Compute Cohen’s d to measure the size of the effect.

What is the variance for this study?

Group of answer choices

7

8

4

2

Answer 1

Given data :

n = 8

x	y	d=x-y	d2
6	2	4	16
8	3	5	25
9	4	5	25
8	1	7	49
10	2	8	64
5	3	2	4
9	8	1	1
7	7	0	0
		= 32	d2 = 184

Sample mean, = d / n

= 32 / 8

= 4

Cohen’s d = / s

= 4 / 2.8284

= 1.4142

variance, s2 = 2.82842

= 8