Data: A MANOVA is performed to study the effect of demand stress and training in behavioral desensitization on communication apprehension. The sample has 2 dependent variables (DVs) and two independent variables (IVs). The first IV has 3 levels, the second IV has 2. These two IVs in factorial arrangement produce 6 cells; 3 participants are assigned to each cell, so there are 3 X 6 = 18 participants in the study. The SPSS data file (stress.sav) is available in Blackboard.
- LMH refers to level of demand stress
- three groups = Low, Moderate, and High (1, 2 and 3);
- TREAT refers to the use of response desensitization vs. instruction in Latin
- two groups = Treatment vs. No Treatment (0 and 1).
Dependent variables (both are reverse coded so that the higher the score the LESS apprehension):
- DV1 writing apprehension and
- DV2 public speaking apprehension
Open the data file in SPSS and follow the following instructions:
- Select ANALYZE/GENERAL LINEAR MODEL/ MULTIVARIATE from the menu;
- Move DV1 and DV2 in the Dependent Variables area and LMH and TREAT in the Fixed Factors area;
- Select Options, then check "Descriptive statistics" and "Effect size estimates" under Display; click Continue;
- In the GLM Multivariate window, click OK.
- EXERCISE. Using the MANOVA described above, answer the following questions:
- What are the Wilk's Lambda coefficients for each main effect and the interaction? (Report the appropriate value, F, df1, df2, p from the Multivariate Tests table)
- How would you interpret these effects?
- Why is the multivariate procedure better in this case than two univariate (ANOVA) tests?
- Given the effects detected, is the sample size in this multivariate ANOVA example adequate?
The question belongs to Statistics and it discusses about performing univariate analysis for the data given.
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