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psy400ch14p364-467
Unequal Variances
| Term | Definition |
|---|---|
| Statistical tests of equality of variances | Levene's test or F test of equality of variances |
| Levene's test and F test of equality of variances | A test of the equality of two variances. |
| Unequal Cell Sizes in Factorial ANOVA Designs | can lead to confounding of experimental effects |
| Lack of Sphericity with Repeated Measures | may increase the probability of a type I error. |
| Mauchly's test of sphericity | tests the sphericity assumption in repeated-measures analysis of variance. |
| In the face ofsphericity violations, you may analyze your data by applying | statistical adjustments such as the Greenhouse-Geisser correction |
| Greenhouse-Geissor correction | adjusts to account for violation of sphericity in repeated measures analysis of variance. |
| Robust statistical methods: | tests that are not greatly affected by conditions that violate the assumptions of standard parametric tests |
| example of assumptions that robust tests are not greatly affected by | nonnormal distribution, the presence of outliers, skewed distributions, or unequal variances |
| Example of a robust statistical method | nonparametric versions of statistical tests such as the Mann-Whitney U test to analyze rank-order data |
| Robust statistical tests may be either | nonparametric or parametric |
| Trimmed mean | computed after removing some fixed percentage (often 10% or 20%) of the largest and smallest values in a data set |
| parametric approaches which estimate specialized parameters, such as a difference in trimmed means | require special procedures for computing important values such as standard errors and confidence intervals |
| BAYESIAN DATA ANALYSIS | prior distribution concerning a hypothesis is combined with experimental data to construct a posterior distribution for the hypothesis. |
| Prior distribution: In Bayesian data analysis, information the experimenter has concerning a statistic or effect prior to running | the experiment. Such prior information may come from previous experiments or a meta-analysis of the relevant literature. |
| In the stroop test a prior distribution might be based on previous experiments. For example, we may have good reason to believe | the difference in mean response times between the interference group and the no-interference group is between 0.5 and 2.0 seconds (likely), — 0.05 and 0.5 (less likely) or 2.0 and 2.5 (quite unlikely) |
| Objective or minimally informative prior: In Bayesian data analysis, a prior distribution that reflects relative ignorance | concerning the value of an experiment effect. For example any difference of mean values from -30 to +30 equally likely |
| Posterior distribution: In Bayesian data analysis, the distribution around a statistic (e.g., mean, difference of means, standard | deviation) that incorporates both prior Information and experimental data |
| Credible interval: In Bayesian data analysis, a range of values from the posterior distribution of a given quantity (e.g.,mean, | difference of means) for which you have a given level of credibility (e.g., 95%) concerning the true value of the quantity |
| Unlike confidence intervals, the 95% credible interval tells us that, based on our prior distribution and our collected data, | there is a 95% chance that the actual difference of means in the population falls between in the interval |