L6 Analyses of Group Differences and Statistical Testing

Flashcards for key terms and definitions related to analyses of group differences, including statistical tests and methodologies.

Chi-Square Test of Independence

A statistical test used to determine whether two categorical variables are independent or associated.

Degrees of Freedom (df)

The number of values in a calculation that can vary independently, calculated as df = (r - 1)(c - 1) where r is the number of rows and c is the number of columns.

Effect Size (Cohen's d)

A measure that quantifies the size of a difference between two means, indicating how many standard deviations the means are apart.

Independent-samples t-test

A statistical method used to compare the means of two independent groups.

Paired-samples t-test

A statistical method used to compare means from the same group at different times or under different conditions.

Null Hypothesis (H₀)

The hypothesis stating that there is no effect or difference; it assumes any observed difference is due to sampling error.

Alternative Hypothesis (H₁)

The hypothesis stating that there is an effect or difference; it posits that the observed differences are due to a factor being tested.

Significance Level (α)

The probability of making a Type I error, set to determine the cutoff for rejecting the null hypothesis.

Chi-Square Statistic (χ²)

A measure used to assess whether observed frequencies in a contingency table deviate from expected frequencies.

Critical Value

The threshold value that the test statistic must exceed in order to reject the null hypothesis at a specified significance level.

Expected Frequencies

The frequencies you would expect in each cell of a contingency table if the null hypothesis is true.

Observed Frequencies (O)

The actual counts recorded in each cell of a contingency table.

Variance Partitioning

The process of expressing total variance in data into different components attributable to different sources.

F-ratio

A ratio used in ANOVA that compares the variance between group means to the variance within the groups.

Effect Size (η²)

The proportion of total variance that is attributed to the treatment effect in ANOVA.

Mann-Whitney U Test

A nonparametric test used to assess whether there is a difference between two independent groups when the outcome variable is ordinal.

Kruskal-Wallis H Test

A nonparametric method for comparing more than two groups with independent samples.

Cramer’s V

A measure of association between two nominal variables, reflecting the strength of association in tables larger than 2x2.