Question

Over the last several years, the average exam grade in social psychology was 86, with a standard deviation of 7. This year, 25 social psychology students have a mean of 82. Are these students different from average social psychology students?

m =

s =

M =

N =

One-tailed or two-tailed?                                            Critical value (with  = .05):

Null Hypothesis (H₀): This sample________________________________________________________

___________________________________________________________________________________

Alternative Hypothesis (H_a): This sample ___________________________________________________

___________________________________________________________________________________

Compute z:

z =                               Reject or fail to reject the null hypothesis?

Interpret result

Answer 1

m = 82, s = 7, M = 86, N = 25

Since we are asking if these students are different from average social psychology students, we use a 2 tailed test.

Null Hypothesis: = 86: The mean exam grade in social psychology this year is equal to 86.

Alternative Hypothesis: 86 : The mean exam grade in social psychology this year is is different from 86.

The Test Statistic:

Z = (m - M) / [s/sqrt(n)] = (82 - 86) / [7/sqrt(25)] = -2.857

The Critical Value: At = 0.05, the left tailed critical value = -1.645

The Decision Rule: If t obsrved is < -1.645, then Reject H0.

The Decision: Since t Observed(-2.857) is < -1.645, Reject H0.

The Conclusion: There is sufficient evidence at the 95% level of significance to conclude that the mean exam grade in social psychology this year is is different from 86.