Exam 15: Introduction to the Analysis of Variance

An investigator conducts an experiment involving the effects of three levels of a drug on memory. Subjects are randomly assigned to one of three conditions. A different drug level is administered in each condition. Memory is measured 10 minutes after each subject receives the drug. The following scores are recorded. The higher the score, the better the memory. The value of F _Scheff is _________.

With one-way, independent groups ANOVA, increasing N causes MS_between to decrease, thereby producing an increase in power.

If k = 2, the t test for independent groups, the F test, and the t test for planned comparisons are all essentially the same test.

A clinical psychologist is interested in comparing the effectiveness of short term relaxation and cognitive-behavioral therapy in treating mild depression. An experiment is conducted in which 15 patients with mild depression are randomly selected and assigned 5 each to a relaxation therapy group, a cognitive/behavioral therapy group, and an attention placebo group. Therapy is administered until the patient is judged no longer depressed or until 10 treatment sessions have elapsed. The following data is obtained. Scores are the number of sessions for each patient. Using a = 0.05, F _crit = _________.

A clinical psychologist is interested in comparing the effectiveness of short term relaxation and cognitive-behavioral therapy in treating mild depression. An experiment is conducted in which 15 patients with mild depression are randomly selected and assigned 5 each to a relaxation therapy group, a cognitive/behavioral therapy group, and an attention placebo group. Therapy is administered until the patient is judged no longer depressed or until 10 treatment sessions have elapsed. The following data is obtained. Scores are the number of sessions for each patient. MS_between = _________.

Tabled F values are one-tailed probability levels.

Define the sampling distribution of F .

The F distribution is a family of curves, each uniquely determined by df.

Which of the following would cause F _obt to increase?

Power is generally the same for the HSD test and the Scheffé test.

In general, if the consequence of making a Type I error were much greater than making a Type II, it would be preferable to use the HSD test rather than the Scheffé test for a post hoc analysis.

Define planned comparisons.

The HSD test uses the t obt statistic.

If F obt is significant, it is possible to tell which groups differ from which without further analysis.

A priori comparisons _________.

Define grand mean ( ).

Doing multiple comparisons following a three group ANOVA with equal n in each group, the critical value of the inference test statistic changes from comparison-to-comparison in the _________.

The alternative hypothesis in an ANOVA can be either directional or nondirectional.

The null hypothesis in the one-way ANOVA asserts that _________.

A clinical psychologist is interested in comparing the effectiveness of short term relaxation and cognitive-behavioral therapy in treating mild depression. An experiment is conducted in which 15 patients with mild depression are randomly selected and assigned 5 each to a relaxation therapy group, a cognitive/behavioral therapy group, and an attention placebo group. Therapy is administered until the patient is judged no longer depressed or until 10 treatment sessions have elapsed. The following data is obtained. Scores are the number of sessions for each patient. Assume you wanted to compare cognitive/behavioral therapy with relaxation therapy, using planned comparisons and a nondirectional H 1 . The obtained value of the appropriate statistic is _________.