Nine students took the sat test their scores are listed belo

Nine students took the sat test. their scores are listed below. later they took a test preparation course and retook the sat. their new scores are listed below. use the wilcoxon signed rank test to test the claim that the test preparation had no effect on their scores. use alpha = .05.

Solution

Wilcoxon Signed Rank Test

variables:

Before - After

4

sum of positive ranks

32

sum of negative ranks

8

n

18.000

expected value

5.745

standard deviation

-2.437

z corrected for ties

.0148

p-value (two-tailed)

No.

Label

Data= Before - After

Rank

1

-20

4.5

2

10

2

3

-40

7.5

4

-30

6

5

-10

2

6

10

2

7

-40

7.5

8

-20

4.5

Null hypothesis: the test preparation had no effect on the test scores.

Alternate hypothesis: the test preparation had effect on the test scores.

The calculated z= - 2.437 < - 1.96, , falls in the rejection region at 0.05 level.

The null hypothesis is rejected.

We conclude that the test preparation had an effect on the test scores.

Wilcoxon Signed Rank Test
		variables:	Before - After
		4	sum of positive ranks
		32	sum of negative ranks
		8	n
		18.000	expected value
		5.745	standard deviation
		-2.437	z corrected for ties
		.0148	p-value (two-tailed)
No.	Label	Data= Before - After	Rank
	1	-20	4.5
	2	10	2
	3	-40	7.5
	4	-30	6
	5	-10	2
	6	10	2
	7	-40	7.5
	8	-20	4.5