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Describe what the positive cross-product () indicates about the first participant's scores relative to the group means, and explain what the final mean of the cross-products () reveals about the overall relationship between sleep hours and alertness.
Case context: A student researcher is investigating the relationship between hours of sleep (: mean = , standard deviation = ) and next-day alertness scores (: mean = , standard deviation = ). A participant has an score of () and a score of (), yielding a cross-product of . Another participant has an score of () and a score of (), yielding a cross-product of . Across the entire sample, the mean of the cross-products is .
Question: Describe what the positive cross-product () indicates about the first participant's scores relative to the group means, and explain what the final mean of the cross-products () reveals about the overall relationship between sleep hours and alertness.
Sample answer: The positive cross-product () indicates that the first participant scored above the mean on both sleep hours and alertness, resulting in two positive scores that multiply to a positive value. The final mean of the cross-products () indicates a positive relationship between sleep hours and alertness, meaning that as sleep hours increase, alertness scores tend to increase as well.
Key points:
- Positive scores correspond to raw values above their respective group means.
- A positive cross-product indicates that a participant's scores deviate in the same direction relative to the means.
- The mean of the cross-products represents Pearson's , with a positive value indicating a positive relationship between the variables.
Rubric: The response must describe that: 1) The positive cross-product shows the participant scored above the mean on both variables. 2) The mean of cross-products () represents a positive correlation, indicating that higher sleep hours are associated with higher alertness scores.
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Research Methods in Psychology - 4th American Edition @ KPU
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