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Based on the calculated probability of their sample results, decide what final conclusion the psychologists should draw regarding the null hypothesis, and justify your answer using the structured logic of hypothesis testing.
Case context: A team of developmental psychologists is evaluating whether a new reading program improves vocabulary scores in elementary students. Following standard procedures, they first assume the null hypothesis is true: that the new program has no effect. After gathering their data, they calculate that the large improvement seen in their sample's vocabulary scores would be extremely unlikely to occur if their initial assumption of no effect were actually true.
Question: Based on the calculated probability of their sample results, decide what final conclusion the psychologists should draw regarding the null hypothesis, and justify your answer using the structured logic of hypothesis testing.
Sample answer: The psychologists should decide to reject the null hypothesis. Because they calculated that their sample results would be extremely unlikely if the null hypothesis were true, the structured logic of hypothesis testing dictates that they use this low probability to reject the initial assumption.
Key points:
- The researchers must decide to reject the null hypothesis.
- The justification relies on the calculated probability being extremely unlikely.
- The final decision to reject or retain is always based directly on the calculated likelihood of the sample results under the initial assumption.
Rubric: Full credit is awarded if the student correctly diagnoses that the researchers should reject the null hypothesis and justifies this decision by explaining that it is based on the extremely low likelihood of the sample results occurring under the initial assumption.
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Research Methods in Psychology - 4th American Edition @ KPU
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