Question

A researcher would like to investigate whether or not there is a difference in IQ between Psychology and History majors. She gathers 16 students (8 whose major is Psychology, and 8 whose major is history) and has them all take an IQ test to test this hypothesis using an alpha level of .01. Below are the data: Psych History

110 90 120 98 100 100 90110 124 100 102 120 110 110 123 120
a. What is the appropriate test?
b. State the null hypothesis:
c. State the alternative hypothesis:
d. Find the critical value:
e. Calculate the obtained statistic:
f. Make a decision:
g. What does your decision mean?

Answer 1

Paired t test

H0 : μd = 0

H1 : μd > 0

Critical value = 3.499

Test statistic = 2.230

Reject H0 if test statistic > Critical value

Kindly check explanation.

Explanation:

Given the data :

110 90 120 98 100 100 90 110

124 100 102 120 110 110 123 120

The hypothesis :

H0 : μd = 0

H1 : μd > 0

Tcritical value, df = n - 1 = 8 - 1 = 7

Tcritical(0.01, 7) = 3.499

The difference, d = (-14,-10,18,-22,-10,-10,-33,-10)

The test statistic :

Xdbar / Sd/√n

The mean difference, Xdbar = Σx / n = - 11.375

The standard deviation of difference, Sd = 14.431

The test statistic :

-11.375 / (14.431/√8) ;

-11.375 / 5.102

= 2.230

Decison :

Reject H0 if test statistic > Critical value

Since ; 2.230 <3.499 ;

We fail to reject the null