Question

Weinstein, McDermott, and Roediger (2010) conducted an experiment to evaluate the effectiveness of different study strategies. One part of the study asked students to prepare for a test by reading a passage. In one condition, students generated and answered questions after reading the passage. In a second condition, students simply read the passage a second time. All students were then given a test on the passage material and the researchers recorded the number of correct answers. a. Identify the dependent variable for this study. b. Is the dependent variable discrete or continuous? c. What scale of measurement (nominal, ordinal, interval, or ratio) is used to measure the dependent variable?

Answer 1

Dependent variable: number of correct answers

Explanation:

The dependent variable is the number of correct answers, because it is the variable that the researchers were recording as response in the experiment.

As it is a counting, it can only take finite values (0 correct answers, 1 correct answer, 2 correct answers and so on). Then, it can be classified as a discrete variable. Discrete values always represent exact quantities that can be counted. For example, number of passengers per car, or number of cows per acre.

Discrete variables can be divided into nominal (they haven’t an order or a hierarchy, as in the example of cows/acre), ordinal (they follow a natural order or hierarchy), interval (they can be divided into classes) or ratio (they represent relative quantities).

The number of correct answers is an ordinal variable, because they have a natural hierarchy. 1 correct answer it’ s better than 0, and 2 corrects answers are better than 1 and 0. Then, you can order your results: 0, 1, 2, 3, 4, etc.