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Identify which type of graph the psychologist should use to display these results, explain why this choice is appropriate based on the nature of the independent variable, and explain what each individual point on this graph represents.

Case context: A psychologist studies how caffeine dosage (measured in milligrams: 100 mg100\text{ mg}, 200 mg200\text{ mg}, and 300 mg300\text{ mg}) affects cognitive processing speed. The researcher wants to display the relationship between these dosage levels and the participants' processing scores using a graph.

Question: Identify which type of graph the psychologist should use to display these results, explain why this choice is appropriate based on the nature of the independent variable, and explain what each individual point on this graph represents.

Sample answer: The psychologist should use a line graph. This choice is appropriate because the independent variable (caffeine dosage) is quantitative and organized into a relatively small number of distinct levels (100 mg100\text{ mg}, 200 mg200\text{ mg}, and 300 mg300\text{ mg}). Each point plotted on this graph represents the mean score on the dependent variable (cognitive processing speed) for participants at that specific dosage level.

Key points:

  • The researcher should choose a line graph to display the data.
  • The independent variable (caffeine dosage) is quantitative and organized into a small number of distinct levels.
  • Each point represents the mean score on the dependent variable (processing speed) for participants at that specific level of caffeine dosage.

Rubric: Full credit is awarded if the response correctly identifies the line graph, justifies it by explaining that the independent variable is quantitative and organized into a small number of distinct levels, and specifies that each point represents the mean score of the dependent variable at each level. Partial credit is given if the graph type is correct but the justification or explanation of the points is incomplete or incorrect.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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