One-Way Analysis of Variance

Question 1

For a one-way analysis of variance (one-way ANOVA), each individual or case must have scores on…

Answer 1

two variables: a factor and a dependent variable.

Question 2

The factor divides individuals into…

Answer 2

two or more groups or levels, whereas the dependent variable differentiates individuals on a quantitative dimension.

Question 3

The ANOVA F test evaluates whether

Answer 3

the population means on the dependent variable differ across the levels of the factor.

Question 4

A one-way ANOVA can be used to analyze data from different types of studies:

Answer 4

Experimental studies, Quasi-experimental studies, Field studies

Question 5

An overall analysis-of-variance test is conducted to…

Answer 5

assess whether means on a dependent variable are significantly different among groups

Question 6

If the overall ANOVA is significant and a factor has more than two levels:

Answer 6

follow-up tests are usually conducted. (These follow-up tests frequently involve comparisons between pairs of group means)

Question 7

if a factor has three levels what might be conducted?

Answer 7

three pairwise comparisons might be conducted to compare the means of groups 1 and 2, the means of groups 1 and 3, and the means of groups 2 and 3. SPSS calls these follow-up tests post hoc multiple comparisons

Question 8

Assumption 1:

Answer 8

The Dependent Variable Is Normally Distributed for Each of the Populations as Defined by the Different Levels of the Factor

Question 9

Assumption 2:

Answer 9

The Variances of the Dependent Variable Are the Same for All Populations

Question 10

Assumption 3:

Answer 10

The Cases Represent Random Samples from the Populations and the Scores on the Test Variable Are Independent of Each Other

Question 11

The General Linear Model procedure computes an effect size index of…

Answer 11

eta squared

Question 12

eta square ranges in value from 0 to 1 which mean…

Answer 12

value of 0 indicates that there are no differences in the mean scores among groups, a value of 1 indicates that there are differences between at least two of the means on the dependent variable and that there are no differences on the dependent variable scores within each of the groups (i.e., perfect replication)

Question 13

eta squared is interpreted as…

Answer 13

the proportion of variance of the dependent variable that is related to the factor.

Question 14

One-way ANOVA assumes…

Answer 14

equality of population variances. If this assumption is violated, use the Browne-Forsythe or the Welch statistic available within One-Way ANOVA in Compare Means

Question 15

Writing APA Results, 1. Describe the statistical test(s

Answer 15

Describe the statistical test(s), the variables, and the purpose of the statistical test(s), Describe the factor or factors, Indicate the number of levels of each factor (description of each level), Describe what the dependent variables are.

Question 16

2. Report the results of the overall test(s).

Answer 16

Describe any decisions about which test was chosen based on assumptions (for a one-way within-subjects ANOVA, justify the choice of using a traditional univariate test instead of a multivariate test), Report the test value and significance level, Report statistics that allow the reader to make a judgment about the magnitude of the effect for each overall test (eta squared),

Question 17

3. Report the descriptive statistics

Answer 17

efer the reader to a table or figure that presents the relevant descriptive statistics (e.g., means and standard deviations for ANOVA designs)

Question 18

4. Describe and summarize the general conclusions of the analysis.

Answer 18

For example, “The results of the one-way ANOVA supported the hypothesis that different types of vitamin C treatment had a differential effect on the reduction of cold symptoms in individuals.”

Question 19

5. Report the results of the follow-up tests

Answer 19

Describe the procedures used to conduct the follow-up tests. Explain any decisions you made about the choice of tests based on their assumptions., Report the method used to control for Type I error across the multiple tests (e.g., Dunnett’s C)., Summarize the results of the follow-up procedures. It may be useful to present the results of the significance tests among pairwise comparisons with a table of means and standard deviations. When possible, report confidence intervals for pairwise comparisons.
Describe and summarize the general conclusions of the follow-up analyses. Make sure to include in your description the directionality of the test. For example, the mean for one treatment group is higher or lower than the mean for another group.

Question 20

6. Report the distributions of the dependent variable for levels of the factor(s)

Answer 20

Report the distributions of the dependent variable for levels of the factor(s) in a graph, if space is available. The graph should be inserted in the text where appropriate. For example, if the graph pertains to assumptions, you would insert it in the section where assumptions are discussed. Likewise, if the graph reflects the means and standard deviations, it should be presented with the delineation of these statistics.