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Based on the definition of a linear relationship, classify the associations found in Study A and Study B. Explain your reasoning for each classification using the characteristics of linear relationships.
Case context: A research methodology student is reviewing scatterplots from two different psychology studies. Study A plots the relationship between 'hours of sleep' and 'number of memory errors', showing points that cluster closely around a straight line sloping downwards. Study B plots 'stress level' and 'task performance', showing points that rise in a straight line initially, but then curve downwards in a U-shape at higher stress levels.
Question: Based on the definition of a linear relationship, classify the associations found in Study A and Study B. Explain your reasoning for each classification using the characteristics of linear relationships.
Sample answer: Study A demonstrates a linear relationship because the data points are reasonably well fit by a single straight line (specifically, a negative correlation). Study B does not demonstrate a linear relationship because the points form a curve (a U-shape) rather than a straight linear trend.
Key points:
- Diagnoses Study A as having a linear relationship.
- Justifies Study A by noting the straight linear trend of the downward slope.
- Diagnoses Study B as not having a linear relationship.
- Justifies Study B by noting that the points form a curve rather than a straight line.
Rubric: The student must correctly identify Study A as a linear relationship (or negative correlation) and Study B as non-linear. The explanation must reference that linear relationships require points to be well fit by a single straight line, not a curve.
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Research Methods in Psychology - 4th American Edition @ KPU
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