2: t-tests Flashcards
What is alpha in relation to the null hypothesis?
The threshold of probability where we are willing to reject the null hypothesis, generally .05.
Type I error
Rejecting the null hypothesis when it is true.
Type II error
Failing to reject the null hypothesis when it is false.
What is the t-ratio?
The difference between means expressed in standard error units.
How is t calculated?
Variance between IV levels
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Variance within IV levels
What are degrees of freedom?
The difference between the number of measurements made and the number of parameters estimate (sample size - parameters).
What are the assumptions for an independent t-test?
Normality, homogeneity of variance, sample size, and independence of observations.
What is Levene’s statistic for?
Looking at the assumption of homogeneity of variance.
What is effect size?
The magnitude of the difference between two IV levels, expressed in SD units.
How is Cohen’s d calculated?
Difference between sample means
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Mean SD
What is a small effect size?
0.2 (85% overlap)
What is a medium effect size?
0.5 (67% overlap)
What is a large effect size?
0.8 (53% overlap)
What variance is absent in a paired t-test?
Individual differences
What are the assumptions for a paired t-test?
Normality (others not relevant).
