Practice Problem Answer: TWO-FACTOR ANOVA

Researchers have sought to examine the effect of various types of music on agitation levels in patients who are in the early and middle stages of Alzheimer's disease. Patients were selected to participate in the study based on their stage of Alzheimer's disease. Three forms of music were tested: Easy listening, Mozart, and piano interludes. While listening to music, agitation levels were recorded for the patients with a high score indicating a higher level of agitation. Scores are recorded below.

1. Complete the following ANOVA table.

   
   

   Source	SS	df	MS	F
   Type of Music	740	2	370.00	49.89
   Degree of Alzheimer's	30	1	30.00	4.05
   Music x Alzheimer's	260	2	130.00	17.53
   Within	178	24	7.42
   Total	1208	29

   
   

2. Graph your data.

   

3. Are there any significant main effects or an interaction effect.

   Test results show that there is a significant main effect for type of music (F=48.89 (2,24), p<.01). However, it appears that there is no significant difference in agitation levels between early and middle stages of Alzheimer's disease (F=4.05 (1, 24), not significant). There is however a significant interaction effect (F=17.53 (2,24), p<.01).

4. Interpret your answer.

   Without post hoc tests, it is not possible to know exactly where the significant differences lie specifically. However, it appears from the graph that patients in both the early and middles stages of Alzheimer's disease experience significantly less agitation while listening to Mozart. Patients in the early stages of Alzheimer's disease exhibited the greatest agitation while listening easy listening musci and patients in the middle stages of Alzheimer's disease exhibited the greated agitation while listening to piano interludes.