Deck 15: Analysis of Variance

Question 1

It is appropriate to conduct a t-Test separately for each paired comparison in a post hoc test.

Answer 1

False

Question 2

Post hoc tests can be employed regardless of whether the F-ratio is significant for the overall data across the multiple groups.

Answer 2

False

Question 3

Suppose a study comparing three group means has 50 cases per group.Which of the following statements is correct about its degrees of freedom (df).

A)The between-groups df is 3.
B)The overall within-groups df is 147.
C)Each group's within-groups df is 47.
D)The overall within-groups df is 149.

Answer 3

The overall within-groups df is 147.

Question 4

MANOVA should be used when more than one dependent variable is involved in an analysis of variance

Question 5

Suppose a study finds a MSBG of 8 and a MSWG o4.The F-Ratio would be:

A)2.0
B)0.5
C)32.0
D)6.0

Question 6

A two-factor ANOVA is conducted to evaluate the effectiveness of exposure therapy in treating civilians and combat veterans who have PTSD.Both groups of clients are randomly assigned to receive either exposure therapy or routine care.A significant interaction effect is found in the two-factor ANOVA.Which of the following interpretations is most appropriate in light of these results?

A)Exposure therapy is more effective than routine care.
B)Both routine care and exposure therapy are effective.
C)The comparative effectiveness of the two treatment conditions varies, depending upon whether the clients are civilians or combat veterans.
D)Routine care is more effective than exposure therapy.

Question 7

A post hoc test is conducted to make multiple comparisons between the mean scores of three groups of clients in a child guidance center.Group A receives play therapy, only.Group B receives family therapy, only.Group C receives both play and family therapy.The significance level is .05.The p value for the difference between Groups A and B is .66.The p value for the difference between Groups A and C is .01.The p value for the difference between Groups B and C is .01.Which of the following interpretations is most appropriate in light of these results?

A)Play therapy and family therapy appear to be equally effective.
B)Play therapy appears to be effective.
C)Family therapy appears to be effective.
D)The combination of play and family therapy appears to be more effective than either play therapy alone or family therapy alone.

Question 8

The F-ratio:

A)Reflects the variation among the means of several groups in relation to the variation within the groups.
B)Contains a numerator that consists of the variation between the means of each group divided by the between groups degrees of freedom.
C)Contains a denominator that consists of the variation in the dependent variable among the individual cases within each group divided by the within groups degrees of freedom.
D)All of these.

Question 9

An analysis of covariance (ANCOVA) is conducted for a study using the pretest and posttest scores of two groups.The F-ratio is statistically significant.What does this mean?

A)There is a significant difference between the two groups on the posttest scores when the effects of the pretest scores are controlled.
B)There is a significant difference between the two groups on the pretest scores when the effects of the posttest scores are controlled.
C)There are significant differences between the two groups on both the pretest and the posttest scores.
D)All of these.

Question 10

ANOVA results without post hoc tests tell us only that there is a statistically significant difference somewhere among the multiple groups being compared -- not which particular comparisons of group means are statistically significant.

Question 11

In a study comparing 4 group means, the number of the between groups degrees of freedom is:

A)The total sample size.
B)One.
C)Three.
D)Four.

Question 12

In a study comparing 4 group means, the F-ratio is statistically significant.This means that:

A)There is a significant difference between each of the four group means.
B)There is a significant difference between at least two of the four groups.
C)The variation within each group is much larger than in results that are not significant.
D)None of these.

Question 13

A two-factor ANOVA identifies the main effect of each independent variable on the dependent variable as well as any interaction effect between the two of them on the dependent variable.

Question 14

The F -ratio will increase when the within group variation increases.

Question 15

It is appropriate to use ANOVA when:

A)We want to compare the means of three or more groups.
B)The dependent variable is at the nominal level of measurement.
C)The dependent variable has three or more categories.
D)The independent variable is at the ratio level of measurement.

Question 16

The degrees of freedom for the numerator in the F -ratio is one less than the number of groups being compared.

Question 17

The ANCOVA procedure examines whether there are significant differences among groups on posttest scores when the effects of the pretest scores or other interval or ratio level variables are controlled.

Question 18

ANOVA can be used only when comparing two means.

Question 19

When evaluating the effectiveness of an intervention, it would be appropriate to conduct a multiple analysis of variance (MANOVA) when:

A)There is more than one dependent variable.
B)We want to avoid inflating the probability of a Type 1 error.
C)The dependent variables being used are correlated with one another in such a way that an intervention will not have significant effects on any one of them alone, but will have a significant effect on a linear combination of them.
D)All of these are reasons for conducting a MANOVA.