In a two-group study, student participants were randomly assigned to either a new math curriculum or business-as-usual control. The researcher measured math achievement at baseline and then again after two months (the primary outcome). The mean score for all participants at baseline was 20. The mean score for all participants at the two month endpoint was 26. The researcher fit an ANCOVA model controlling for baseline score. The prediction equation shown below, where Gi represents group (0 = control, 1 = treated), and Xi represents baseline score. According to the fitted model, what is the adjusted mean of the treated group? \(\hat{Y}_i = 3.5 + 4.6G_i + 0.7X_i\)

Based on the plot, it is reasonable to expect the F statistic based on ANCOVA to be larger than the F statistic based on ANOVA for the omnibus test of group mean differences.

Which conclusion is most appropriate?

There is a main effect for factor B

The effect size measure Cohen’s d represents the number of pooled standard deviations by which two group means differ.

Data shown below correspond with which experimental design?

Suppose interest centers on a test of the mean of the first group against the average of the means of the other two groups. If the researcher defines a contrast ψ = c1µ1 +c2µ2 + c3µ3 and tests H0 : ψ = 0, the values c1 = 1, c2 = −1, c3 = −1 correspond with a test of the desired hypothesis.

What is the main purpose of an introduction paragraph?

A five-paragraph essay includes an introduction, body paragraphs, and a conclusion.

What is the purpose of a hook in the introduction?