Significance Testing Principles

• Data Collection: The Inter-university Consortium for Political and Social Research (ICPSR)

The ICPSR provides access to a large repository of social science and political data. Data sets can be constructed and downloaded for use in most popular statistical packages.
• 2 x 2 Contingency Tables

This applet simulates experiments using 2 x 2 contingency tables. You specify the population proportions and the sample size and examine the effects on the probability of rejecting the null hypothesis.
• Robustness of t test and ANOVA

This applet lets you explore the effect of violations of the assumptions of normality and homogeneity of variance on the type I error rate and power of t tests (and two-group analysis of variance).
• Smiles and Leniency

This case study addresses the question: "Will a smiling person accused of a crime be treated more leniently than one who is not smiling? If so, does the type of smile make a difference?" It concerns the following concepts: quantile/boxplots, contrasts among means, Dunnett's test, and Bonferroni correction.
• Physicians' Reactions to Overweight Patients

This case study assesses the question, "Do physicians discriminate against overweight patients?" This study indicates that, at least in one respect, they do. Concepts: t-test, means, boxplots
• Against All Odds: 28. Inference for Proportions

This free online video program "marks a transition in the series: from a focus on inference about the mean of a population to exploring inferences about a different kind of parameter, the proportion or percent of a population that has a certain characteristic. Students will observe the use of confidence intervals and tests for comparing proportions applied in government estimates of unemployment rates."
• DAU StatRefresher: Random Variables

This tutorial on Random Variables helps students understand the definition of random variables, recognize and use discrete random variables, recognize and use continuous random variables, and solve exercise problems using random variables.
• DAU StatRefresher: Data Analysis

This is an interactive tutorial on Data Analysis topics including representations of data, understand the definition of mean, understand the definition of variance, recognize a few other useful concepts, recognize various sampling techniques, and solve exercise problems using data analysis.
• DAU StatRefresher: Moving Averages

This tutorial includes using, finding, weighting, and solving problems with Moving Averages.
• Video: Against All Odds: 25. Tests of Significance

This free online video program "explains the basic reasoning behind tests of significance and the concept of null hypothesis. The program shows how a z-test is carried out when the hypothesis concerns the mean of a normal population with known standard deviation. These ideas are explored by determining whether a poem "fits Shakespeare as well as Shakespeare fits Shakespeare." Court battles over discrimination in hiring provide additional illustration.