You are testing the claim that the mean GPA of night students is less than the mean GPA of day students.

-Sample 1: You sample 55 night students, and the sample mean GPA is 2.84 with population standard deviation of 0.92

-Sample 2: You sample 20 day students, and the sample mean GPA is 2.91 with population standard deviation of 0.83

Calculate the z-test statistic, please keep at least 6 decimal places during the calculation.

Hint: Use the test statistic formula:z

=

(

x

1

x

2

)

(

1

2

)

2

1

n

1

+

2

2

n

2

z=(x1-x2)-(1-2)12n1+22n2

, (Note:

1

2

1-2

= 0)