Question

A major university would like to improve its tarnished image following a large on-campus scandal. Its marketing department develops a short television commercial and tests it on a sample of n = 10 subjects. People's attitudes about the university are measured with a short questionnaire both before and after viewing the commercial. The data are as follows:

Person	X1 (Before)	X2 (After)
A	15	15
B	11	13
C	10	18
D	11	12
E	14	16
F	10	10
G	11	19
H	10	20
I	12	13
J	15	18

(a) Is this a within-subjects or a matched samples design? Explain your answer.

(b) Conduct a hypothesis test (showing all five steps) to determine if the university should spend money to air the commercial (i.e., did the commercial improve the attitudes?) Assume an alpha level = 0.05. Use SPSS and provide pictures of the data that you get in SPSS.

Answer 1

a) This is a matched sample design because it has a seperate experimental group and we need to match every subject of before with the after, that is why it is a matched sample design.

b)

The hypothesis would be as followed:

H₀ : µ₁-µ₂=0

H₁ : µ₁-µ₂≠0

Using SPSS, analysis would be as followed:

1-> First input data set as followed:

Name Width Decimals Values Туре String Label Missing Columns Align Measure Role Nominal Input Person None 8 Left 1 0 None Scale Input iRight 2 X1 Numeric 2 Before None None Input X2 8 2 After None None 8 iRight Scale Numeric 4 5 6

2-> It would be as followed:

Person X1 X2 var 15.00 15.00 А 2 в 11.00 13.00 10.00 18.00 12.00 11.00 16.00 5 14.00 6 F 10.00 10.00 7 11.00 19.00 8 н 10.00 20.00 12.00 13.00 10 15.00 18.00 J

3-> Now, for analysis go to 'ANALYZE'->'COMPARE MEANS'->'PAIRED SAMPLES T-TEST'-> then put the data you have input in step 2

4-> Analysis would be as followed:

As you can look into the above results,

T-TEST PAIRS=X1 WITH X2 (PAIRED) /CRITERIA CI(.9500) /MISSING ANALYSIS. T-Test [DataSet0] Paired Samples Statistics Std. Error Mean Std. Deviation Mean Pair 1 Before 11.9000 10 2.02485 .64031 After 15.4000 10 3.33999 1.05620 Paired Samples Correlations N Correlation Sig. Pair 1 Before & After 773 10 .105 Paired Samples Test Paired Differences 95% Confidence Interval of the Difference Std. Error Std, Deviation Lower Upper Mean Mean df Sig. (2-tailed) Before -After Pair 1 -3.50000 -6.16064 -.83936 3.71932 1.17615 -2.976 .016

p-value= 0.016

p-value<alpha-value

0.016<0.05

Hence, we may reject the null hypothesis.