ch. 9 studyguide

# ch. 9 studyguide - 1 When would you use an ANOVA rather...

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1. When would you use an ANOVA rather than a t test? An ANOVA would be used rather than a t test when there are more than two levels to the independent variable(s). For example, if an independent t test was done comparing two different nationalities to see which one scored better on an exam, one would have to use an ANOVA test if there were three different nationalities being compared. 2. What are the null and alternative hypotheses for ANOVAs? For ANOVAs, the null hypothesis will always state that all of the means are equal to each other (Ho: μ=μ=μ). The alternative hypothesis will always state that there is a difference between at least two of the means. 3. Which of the two estimates of population variance depends on whether the null hypothesis is true? Why? The between-groups estimate of the population variance depends on whether the null hypothesis is true because that is the estimate the focuses on the variation between the different distributions. The within-groups estimate only focuses on the variation within one distribution which is not mentioned in the null hypothesis. 4. Describe the differences between within-groups estimations of population variance and between- groups estimations of population variance. As mentioned previously, the within-groups estimations of population variance describes the variance within each population. It does not depend on the null hypothesis and it gives no information about the variances between one population and another. The between-groups estimations of population variance describe the variance between all of the populations. These do depend on the null hypothesis and it does give information about the variances between the populations. For instance, when the null hypothesis is true, remember we said that all of the means are equal to each other. This means that the variability between the means is no different than the variability that is normally seen within each population. This also means that in order to determine

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## This note was uploaded on 05/05/2011 for the course PSY 293 taught by Professor Dr.hall during the Fall '09 term at Miami University.

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ch. 9 studyguide - 1 When would you use an ANOVA rather...

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