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Case Study

Evaluate this research scenario to determine the appropriate statistical test and formulate the precise null and alternative hypotheses. Justify your choice based on the structure of the study.

Case context: A health psychologist investigates the accuracy of university students' estimates of the number of calories in a standard chocolate chip cookie. The actual number of calories in the cookie is 250. The psychologist collects calorie estimates from a sample of students and computes the sample mean (MM).

Question: Evaluate this research scenario to determine the appropriate statistical test and formulate the precise null and alternative hypotheses. Justify your choice based on the structure of the study.

Sample answer: The appropriate statistical test is a one-sample tt-test. This is justified because the study compares a single sample mean (MM, the students' average estimate) to a specific, known hypothetical population mean (μ0=250\mu_0 = 250 calories), which serves as a standard of comparison. The null hypothesis should be formulated as μ=250\mu = 250 (meaning the population's true mean estimate equals the actual calorie count), and the alternative hypothesis should be formulated as μ250\mu \neq 250 (meaning the true population mean estimate differs from the actual count).

Key points:

  • Selects the one-sample tt-test.
  • Identifies the hypothetical population mean (μ0\mu_0) as 250.
  • Formulates the null hypothesis as μ=250\mu = 250.
  • Formulates the alternative hypothesis as μ250\mu \neq 250.
  • Justifies the test by stating it compares a single sample mean against a specific standard of comparison.

Rubric: A full credit response correctly identifies the one-sample tt-test, accurately formulates the null and alternative hypotheses using 250 as μ0\mu_0, and justifies the choice by referencing the comparison of a single sample mean to a specific hypothetical standard.

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Updated 2026-05-27

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Research Methods in Psychology - 4th American Edition @ KPU

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