Question

You are interested in whether a study intervention significantly affects students’ grades on a statistics exam. You recruit a sample of 36 students from a normally distributed population with µ = 75 and s = 7.5. You chose an alpha level of .05 and perform a two-tailed hypothesis test. After participating in the study intervention, the students’ statistics exam average is 79. Perform a z-test to determine whether the study intervention significantly affected students’ exam grades. (0.5 points)

a) After performing the z-test, we determined that the study intervention did not significantly affect the exam grades.

b) After performing the z-test, we determined that the study intervention significantly decreased exam grades.

c) After performing the z-test, we determined that the study intervention significantly increased exam grades.

Answer 1

Test statistics

z = ( - ) / ( S / sqrt(n) )

= ( 79 - 75) / ( 7.5 / sqrt(36) )

= 3.2

This is test statistics value.

Two tailed critical value = -1.96 , 1.96

One tailed critical value = 1.645

Since test statistics > 1.645, we have sufficient evidence to conclude that average is increased.

After performing the z-test, we determined that the study intervention significantly increased exam grades.