Question

An educational psychologist hypothesized that presenting learning material in a hypertext form would result in better learning than traditional text. Hypertext is electronic text containing key words that are hyperlinks, so that when they are clicked the reader moves to a portion of the text describing the key word. In this way, a reader can move about the text at will studying various topics by clicking on key words. In contrast, traditional text requires a student to read through the material in a fixed, linear fashion. The psychologist also wanted to compare hyperlinks that were structured after an expert’s knowledge of the domain with randomly structured hyperlinks.

He randomly assigned 45 astronomy students to three learning conditions: Expert Hypertext, Random Hypertext, and Normal Text, which he designated as as A1, A2, and A3, where they read and studied material on star formation. The dependent variable was scores on an exam over the studied material. Please download the Excel file attached the first question to see the results of the study. The psychologist performed an ANOVA on the data to test his hypothesis.

What was the null hypothesis being tested? What are the degrees of freedom (df) for the study?

Answer 1

The null hypothesis stated there are no differences between three learning conditions, and the degrees of freedom for the study are 2 (between groups) and 42 (within groups).

Step-by-step explanation:

The null hypothesis being tested in the educational psychology experiment described would be that there is no significant difference in learning outcomes (as measured by scores on an exam over the studied material on star formation) between the three different learning conditions: Expert Hypertext (A1), Random Hypertext (A2), and Normal Text (A3). The degrees of freedom in an ANOVA test are calculated based on the number of levels in the independent variable and the total number of observations.

Since there are three groups (A1, A2, A3), the degrees of freedom for the 'between groups' (dfbetween) would be the number of groups minus one (3 - 1 = 2). The degrees of freedom for the 'within groups' (dfwithin) would be the total number of observations minus the number of groups (45 - 3 = 42).