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17 Cards in this Set
- Front
- Back
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In what situation do we use analysis of variance?
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When comparing three or more groups to see if they come from the same population.
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How does ANOVA establish whether groups are from the same population?
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ANOVA compares how spread out groups are from each other relative to how spread out individuals are within groups.
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What two estimates of the population variance are compared in ANOVA?
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Between-groups variance (spread among groups) and within-groups variance (spread among individuals).
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What does between-groups variance tell us?
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How spread out groups are from each other.
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What does within-groups variance tell us?
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How spread out individuals are within groups.
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In calculating between-groups variance, what does "n" represent?
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The number of cases in any *one* group.
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What is the grand mean?
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The average of the group means.
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How do you calculate the within-groups variance?
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Take the average of the population variance estimates from all groups.
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What is the F-ratio?
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The comparison of between-groups variance to within-groups variance.
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How do you calculate the between-groups degrees of freedom?
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Number of groups - 1
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How do you calculate within-groups degrees of freedom?
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Add up the degrees of freedom from each group.
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What is another term for "between-groups degrees of freedom"?
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Numerator degrees of freedom
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What is another term for "within-groups degrees of freedom"?
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Denominator degrees of freedom
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How do you calculate the variance of the means?
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Divide the sum of squared deviations of the sample means from the grand mean by the number of groups minus one.
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How do you calculate the between-groups variance?
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Multiply the variance of the means by the number of cases in any *one* group (n).
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What does it mean when you have a large F ratio?
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Groups are more spread out than individuals, so group membership has an effect on the variable of interest.
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What does it mean when the F-ratio is small?
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The groups are not very spread out, so any variability is likely to be random error among individuals. There is likely not any group effect on the variable of interest.
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