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Who developed the ANOVA?
R.A. Fischer
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When can an ANOVA be used?
- In place of the T test for designs with 2 conditions
- Designs with more than 2 conditions
- Designs with more than one IV
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What can we view the ANOVA as?
- A model fitting procedure
- AND a hypothesis testing procedure
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What is the SStotal?
A measure of the variability for scores and residuals around a single mean
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What is the SSe?
A measure of the variability of residuals and scores around the mean of each condition
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What is the SSmodel?
The difference between the SStotal and SSe
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What does the SSmodel represent?
The signal component in the data (the variability between the condition means)
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What are SSmodel and SSe also known as?
- SSbetween (groups)
- SSwithin (groups)
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What are the assumptions for the anova?
The same as for any other parametric test (normality an homogeneity)
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What are the mean squares (MS) in anovas?
Variances in the data (confusingly)
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How do we find the MS?
Divide the SS with the degrees of freedom
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What is the DF total?
Total number of scores in the experiment minus 1
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What is the DF model?
- The number of experimental conditions -1
- Experimental conditions = k
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What is the DF error?
The degrees of freedom for the first condition minus the DF for the second one
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What is the F value?
- The test statistic
- Named after Fischer (gay)
- The ratio of the two variances or mean squares
- (MS model over MS error)
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What are the degrees of freedom for the F ratio?
The DF for the model and error
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When the null is true, what is the expected F value?
1.0
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When there is a high F value, what can be inferred?
- An experimental effect is present
- This could be du to chance though
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How is the F-distribution different from the t-distribution?
- It is positively skewed
- Only the upper tail is used when testing hypotheses (even in 2 sided tests)
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