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11 Cards in this Set
- Front
- Back
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What is ANOVA? |
An extension of the t-test, whereby data is analysed from research designs that are more complex than 2 conditions Where t-test measures 2 levels of 1 IV, one-way ANOVA measures 3 levels of 1 IV |
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What does ANOVA calculate? |
• Means for each group • Grand mean for entire sample • Within-groups variation • Between-groups variation *The last 2 provide us with the F-ratio |
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What is the F-ratio? |
Between-groups variance / Within-groups variance In other words, it is the variance explained by the model / residual variance not explained by the model |
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What are some differences between F-statistics and t-statistics? |
• F-statistic cannot be negative • ANOVA squares all of the values -> value of F is the square of the value of t • ANOVA is a one-tailed test • If one wanted to explore a directional hypothesis using ANOVA, we would have to conduct follow-up analyses |
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How does mean difference and variance affect F-statistic? |
If mean difference is large: F-statistic is larger, p-value is smaller If variance is large: F-statistic is smaller, p-value is larger |
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What is sum of squares? |
The sum of the squared deviations of scores from their mean value |
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What is a mean square? |
Refers to the variance in the data due to a particular source of variation |
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Why are comparisons of conditions needed in tests? |
Results of a statistical test with >2 conditions will often shown a significant result but not where the difference lies A comparison of conditions is needed to see which ones are causing the effect: • Pairwise comparison - Comparing them two at a time • Post hoc comparison - Performing unplanned comparisons after discovering the significant findings *Contrasts = planned comparisons |
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What is main effects? |
The effect of a factor (IV) on the DV in an analysis of variance measured without regard towards the other factors in the analysis |
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What is the Tukey test? |
Similar to the t-test, it calculates: (difference between any two means) / (standard error of the difference between any two means) Overcomes increased risk of Type I error by setting an overall level of significance |
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What is meant by the term ‘sphericity’? |
As Levenes’ test is a test for homogeneity of variance in between-participants ANOVA, sphericity is the equivalent data assumption when running a within-participants ANOVA The sphericity assumption: The variance in the differences between each condition will be the same |
