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A researcher states that because they found their sample mean (M=7.1M = 7.1) is numerically different from the hypothetical comparison mean (μ0=7.0\mu_0 = 7.0), they can automatically reject the null hypothesis (μ=μ0\mu = \mu_0) without running a statistical test. Evaluate this statement. Explain whether the researcher's decision is justified and why a one-sample tt-test is necessary.

Question: A researcher states that because they found their sample mean (M=7.1M = 7.1) is numerically different from the hypothetical comparison mean (μ0=7.0\mu_0 = 7.0), they can automatically reject the null hypothesis (μ=μ0\mu = \mu_0) without running a statistical test. Evaluate this statement. Explain whether the researcher's decision is justified and why a one-sample tt-test is necessary.

Sample answer: The researcher's decision is not justified. A simple numerical difference in a sample mean does not prove that the true population mean (μ\mu) differs from the comparison mean (μ0\mu_0), as this difference could be due to random sampling error. A one-sample tt-test is necessary to evaluate whether the observed difference is statistically significant rather than just a result of random chance.

Key points:

  • Evaluate the researcher's decision as unjustified or incorrect.
  • Explain that sample means naturally deviate from the comparison mean due to random sampling error.
  • Explain that a one-sample tt-test is necessary to determine if the difference is statistically significant.

Feedback: The response should evaluate the researcher's claim as unjustified, explaining that sample means naturally vary from the true population mean due to random sampling error, and that a one-sample tt-test is required to determine whether the difference is statistically significant.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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