Sally is interested in studying the relationship between height and GPA. To inve

Question

Sally is interested in studying the relationship between height and GPA. To investigate this question, she went to her University’s gym and took a survey of students there at the time. She found that height was negatively correlated with GPA. Sally uses these results to make the claim, “The taller you are, the less intelligent you are”. Is this a valid claim to make based on her study? How do you evaluate the internal and external validity of the study? Suggest at least one way that Sally could improve her study and explain why your improvement would enhance either the internal validity, external validity, or both

Explanation / Answer

Firstly, to check whether the claim made by Sally is valid, statistical significance test of null hypothesis rheight GPA =0 has to be done. If the test statistic t, falls in critical region, reject null hypothesis to claim that there is significant correlation among height and GPA and the claim is valid.

As far as internal validity i sconcerned, find if there exists any confounding variable in the study, which Sally has successfully eliminated. To check for external validity, one has to make sure sufficient sample size is taken at random and the correlation coefficient is computed followed with regression analysis for which the result can be generalized to population at large.

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