Case Study

Explain why the student's proposed bar graph setup is inappropriate for presenting the results of this factorial design based on standard graphing conventions. Describe what type of graph should be used instead and how the variables should be correctly arranged on it.

Case context: A research group is preparing to present the results of a factorial study that investigated the impact of two independent variables on student learning. The first independent variable is 'Number of Practice Sessions' (with levels: 1, 2, 3, or 4 sessions), which is a quantitative variable. The second independent variable is 'Feedback Type' (with levels: Praise vs. Constructive Criticism), which is a categorical variable. A student researcher proposes using a bar graph to plot the results, placing 'Feedback Type' on the xx-axis and representing the 'Number of Practice Sessions' using four different colored bars.

Question: Explain why the student's proposed bar graph setup is inappropriate for presenting the results of this factorial design based on standard graphing conventions. Describe what type of graph should be used instead and how the variables should be correctly arranged on it.

Sample answer: The student's proposed bar graph is inappropriate because when a factorial design includes a quantitative independent variable ('Number of Practice Sessions'), a line graph should be used instead of a bar graph. In a proper line graph setup, the quantitative variable ('Number of Practice Sessions') should be placed on the xx-axis, while the categorical variable ('Feedback Type') should be represented by distinct line formats. The student's proposal incorrectly treats the quantitative variable as categorical bars and places the categorical variable on the xx-axis.

Key points:

  • Identifies that a line graph is appropriate because the design includes a quantitative variable ('Number of Practice Sessions').
  • Explains that the quantitative variable should be plotted along the xx-axis.
  • Explains that the categorical variable ('Feedback Type') should be represented by distinct line formats.
  • Recognizes that the student's proposal incorrectly uses a bar graph and misplaces the variables.

Rubric: The response must explain that a line graph is preferred over a bar graph because one of the variables is quantitative. It must correctly specify that the quantitative variable ('Number of Practice Sessions') goes on the xx-axis, and the categorical variable ('Feedback Type') must be shown using distinct line formats.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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