Question

# Do students reduce study time in classes where they achieve a higher midterm score? In a...

Do students reduce study time in classes where they achieve a higher midterm score? In a Journal of Economic Education article (Winter, 2005), Gregory Krohn and Catherine O’Connor studied student effort and performance in class over a semester. In an intermediate macroeconomics course, they found that “students respond to higher midterm scores by reducing the number of hours they subsequently allocate to studying for the course”. Suppose that a random sample of n=8 students who performed well on the midterm exam was taken and weekly study times before and after the exam were compared. The resulting data are given in excel workbook Homework 4 page 1. Assume that the population of all possible paired differences is normally distributed. Can it be confirmed that students reduce their study time after earning a high midterm grade? Use α =0.05. Complete the hypothesis test in excel and write out the hypotheses being tested, the value of the test statistic, critical value, p-value and the complete conclusion including your alpha level, test statistic value and p-value.

 Students 1 2 3 4 5 6 7 8 Before 15 14 17 17 19 14 13 16 After 9 9 11 10 19 10 14 10

 Before After Difference 15 9 6 14 9 5 17 11 6 17 10 7 19 19 0 14 10 4 13 14 -1 16 10 6

Sample mean of the difference using excel function AVERAGE(), x̅d =    4.1250

Sample standard deviation of the difference using excel function STDEV.S(), sd =    2.9970

Sample size, n =    8

Null and Alternative hypothesis:

Ho : µd ≤ 0 ; H1 : µd > 0

Test statistic:

t = (x̅d)/(sd/√n) = (4.125)/(2.997/√8) = 3.8930

df = n-1 = 7

Critical value :

Right tailed critical value, t-crit = ABS(T.INV(0.05, 7)) = 1.895

Reject Ho if t > 1.895

p-value :

Right tailed p-value = T.DIST.RT(3.893, 7) = 0.0030

Decision:

p-value < α, Reject the null hypothesis

Conclusion:

There is enough evidence to conclude that the students reduce their study time after earning a high midterm grade at α = 0.05.

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