One-way analysis of variance, or one-way ANOVA, is used to assess whether the population means of several groups differ. Although the question concerns means, the test uses variation in the data to evaluate the evidence. This lesson explains the purpose of the test, its five assumptions, and how to state and interpret its hypotheses.
A one-way ANOVA compares the means of three or more groups defined by one categorical factor. For example, a business might compare average customer spending across several store locations. The factor is store location, and the response is spending.
All flashcards
What does a one-way ANOVA test?
Whether the population means of three or more groups defined by one categorical factor are all equal.
What are the five basic assumptions or requirements of one-way ANOVA?
Normal populations; randomly selected and independent samples; equal population variances; a categorical factor; and a numerical response.
How is the null hypothesis written for k groups?
H0:μ1=μ2=⋯=μk. It states that all group population means are equal.
What does a significant omnibus ANOVA result establish?
At least one pair of population means differs, but the result alone does not identify which pair.
Why does ANOVA use variance to test differences among means?
Differences among group centers add variation to the combined data. ANOVA compares variation among groups with variation within groups.
Quiz questions
What is the main purpose of a one-way ANOVA?Answer: Compare means across three or more groups defined by one categorical factor.
If a one-way ANOVA result is significant, what can be concluded from that result alone?Answer: At least one pair of population means differs, but the pair is not identified.
Which condition about population variability is assumed by a basic one-way ANOVA?Answer: The population variances are equal across groups.
Which sampling condition is assumed in a basic one-way ANOVA?Answer: Samples are randomly selected and independent of one another.
What distributional assumption does a basic one-way ANOVA make about the populations?Answer: Each population is assumed to be normally distributed.