Question

A social psychologist conducts an experiment to determine the best way to design a message for college students about the importance of engaging in safe sex. She hypothesizes that two factors impact the effectiveness of the message: (a) the medium used to deliver the message (lecture, video, or pamphlet), and (b) the emotional tone of the message (fear, neutral, or humor). The dependent variable is a measure of behavioral intention to engage in safe sex behavior (higher score indicating greater intention). She randomly assigns 45 participants to 9 groups, and obtains the following data:

Emotional Tone	Lecture	Video	Pamphlet
Fear	7 6 7 4 4	6 5 7 6 4	5 4 7 4 6
Neutral	6 9 8 4 2	6 4 7 5 6	6 4 5 8 4
Humor	7 7 4 8 4	4 2 1 2 1	8 5 4 6 4

a. Using Excel, analyze these data by performing a two-way between-groups ANOVA. Create formulas to calculate the SS terms and the rest of the ANOVA summary table.

b. Include the effect size (eta-squared) for the medium, emotional tone, and medium X emotional tone effects in your ANOVA table (you’ll need to create your own formulas).

c. Create a graph to show the results, with error bars (estimated standard error of the means).

d. Insert a textbox in which you report the results of the ANOVA, the effect sizes for any significant effects, and refer to the graph to describe the pattern of any significant results.

Answer 1

(a) The ANOVA table is:

			Factor 2
	Means:
		Lecture	Video	Pamphlet
	Fear	5.6	5.6	5.2	5.5
Factor 1	Humor	5.8	5.6	5.4	5.6
	Row 3	6.0	2.0	5.4	4.5
		5.8	4.4	5.3	5.2
	5	replications per cell
ANOVA table
Source	SS	df	MS	F	p-value
Factor 1	11.51	2	5.756	2.04	.1449
Factor 2	15.24	2	7.622	2.70	.0807
Interaction	32.22	4	8.056	2.85	.0375
Error	101.60	36	2.822
Total	160.58	44

(b) The effect sizes are:

ANOVA table
Source	SS	df	MS	F	p-value	eta-squared
Factor 1	11.51	2	5.756	2.04	.1449	0.0716856
Factor 2	15.24	2	7.622	2.70	.0807	0.094935
Interaction	32.22	4	8.056	2.85	.0375	0.2006643
Error	101.60	36	2.822
Total	160.58	44

(c) The graphs are:

(d) The results are:

ANOVA table
Source	SS	df	MS	F	p-value	Significance
Factor 1	11.51	2	5.756	2.04	.1449	not significant
Factor 2	15.24	2	7.622	2.70	.0807	not significant
Interaction	32.22	4	8.056	2.85	.0375	significant
Error	101.60	36	2.822
Total	160.58	44