Question

1. Music seems to be everywhere in society, and psychologists have investigated its effects on a variety of performances. For example, suppose an experimenter created three equivalent groups of eight people each and asked each person to perform a proofreading task on a short research paper. Subjects in group A1 performed the task with no music playing in the background, subjects in group A2 performed the task with a selection of oldies playing in the background, and subjects in groups A3 performed the task while listening to hard rock. The dependent variable was the errors detected out of a possible 50. Suppose the following scores were obtained:

No Music (A1)	Oldies (A2)	Hard Rock (A3)
40	34	26
41	39	24
39	38	19
36	40	23
35	34	18
32	35	21
31	29	23
34	36	29

1.a.Analyze the scores with a one-factor between-subjects ANOVA to answer the question: Did the music condition affect the number of errors detected by a subject? Use α= .05. If needed, use the Tukey HSD test for multiple (pairwise) comparisons.

1.b.Report the results of this experiment as it would appear in a research paper.

Answer 1

1.a.Analyze the scores with a one-factor between-subjects ANOVA to answer the question: Did the music condition affect the number of errors detected by a subject? Use α= .05. If needed, use the Tukey HSD test for multiple (pairwise) comparisons.

MINITAB used

One-way ANOVA: No Music, Oldies, Hard Rock

Method

Null hypothesis	All means are equal
Alternative hypothesis	Not all means are equal
Significance level	α = 0.05

Equal variances were assumed for the analysis.

Factor Information

Factor	Levels	Values
Factor	3	No Music, Oldies, Hard Rock

Analysis of Variance

Source	DF	Adj SS	Adj MS	F-Value	P-Value
Factor	2	893.3	446.63	34.39	0.000
Error	21	272.8	12.99
Total	23	1166.0

Model Summary

S	R-sq	R-sq(adj)	R-sq(pred)
3.60390	76.61%	74.38%	69.45%

Means

Factor	N	Mean	StDev	95% CI
No Music	8	36.00	3.70	(33.35, 38.65)
Oldies	8	35.63	3.50	(32.98, 38.27)
Hard Rock	8	22.88	3.60	(20.23, 25.52)

Pooled StDev = 3.60390

Tukey Pairwise Comparisons

Grouping Information Using the Tukey Method and 95% Confidence

Factor	N	Mean	Grouping
No Music	8	36.00	A
Oldies	8	35.63	A
Hard Rock	8	22.88		B

Means that do not share a letter are significantly different.

Tukey Simultaneous Tests for Differences of Means

Difference of Levels	Difference of Means	SE of Difference	95% CI	T-Value	Adjusted P-Value
Oldies - No Music	-0.38	1.80	(-4.91, 4.16)	-0.21	0.976
Hard Rock - No Music	-13.13	1.80	(-17.66, -8.59)	-7.28	0.000
Hard Rock - Oldies	-12.75	1.80	(-17.29, -8.21)	-7.08	0.000

Individual confidence level = 98.00%

1.b.Report the results of this experiment as it would appear in a research paper.

The 8 participants in the No Music group had an average number of error of 36.0 (SD = 3.7); the 8 participants in the Oldies group had an average error of 35.6 (SD = 3.5), and the 8 participants in the Hard Rock group had a mean of 22.9 (SD = 3.6). The effect of music therefore, was highly significant, F(2,21) = 34.4, p<.001.

Post hoc comparisons using the Tukey HSD test indicated that the mean error for the Hard Rock was significantly different than the No music and Oldies . However, the Oldies did not significantly differ from the No music conditions.