To test whether extracurricular activity is a good predictor of college success,

Question

To test whether extracurricular activity is a good predictor of college success, a college administrator records whether students participated in extracurricular activities during high school and their subsequent college freshman GPA. (a) Code the dichotomous variable and then compute a point-biserial correlation coefficient. (b) Using a two-tailed test at a 0.05 level of significance, state the decision to retain or reject the null hypothesis. Retain the null hypothesis. Reject the null hypothesis.

Explanation / Answer

a)

Point Biserial correlation is r-square = -0.41

b)

t = sqrt((n-2) / (1 - r-square))

      = SQRT(10-2/(1-(-0.41)^2))

    = 3.10

Critical value with 8 degrees of freedom is 2.306

Since the calulated value is 3.10 greater than the critical value 2.306, Hence we reject null hypothesis.

Ans: reject null hypothesis.

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