Short Answer

If a researcher obtains a sample mean of 200200 calories and a 95%95\% confidence interval of 160160 to 240240 for a cookie calorie estimation task, apply this information to evaluate the claim that the true population mean is 250250. State whether this claim is statistically significantly different at the .05.05 alpha level and explain why.

Question: If a researcher obtains a sample mean of 200200 calories and a 95%95\% confidence interval of 160160 to 240240 for a cookie calorie estimation task, apply this information to evaluate the claim that the true population mean is 250250. State whether this claim is statistically significantly different at the .05.05 alpha level and explain why.

Sample answer: The claim of a population mean of 250250 is statistically significantly different from the sample mean at the .05.05 alpha level. This is because 250250 falls outside the 95%95\% confidence interval range of 160160 to 240240.

Key points:

  • Applies the interval limits to determine if 250250 is inside or outside the range.
  • Concludes that the value 250250 is statistically significantly different at the .05.05 alpha level.
  • Justifies the decision based on the value falling outside the 160160 to 240240 range.

Rubric: The response must correctly apply the decision rule to identify that the value 250250 is statistically significantly different at the .05.05 level because it lies outside the confidence interval limits of 160160 to 240240.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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