Question

1. At a college a popular achievement test is used for advanced college placement.   Counselors selected a random sample of 100 students from the college and scored their tests by hand before sending them in for computer processing.  For this sample, the mean was 525 and s = 25.  A 99% confidence interval for the mean is:

1. (460.6, 589.4)     b)  (518.56, 531.44)   c) (520.1, 529.9)     d) (476, 574)    

Answer 1

Given,

X_bar = 525

s = 25

n = 100

Now calculate 99% confidence interval is

CI = x_bar z*(s/n)

z value for 99% confidence interval is 2.576.

CI = 525 2.576*(25/100)

= 525 6.44

CI = 525 - 6.44 and CI = 525 + 6.44

= 518.26 and CI = 531.44

Therefore 99% confidence interval is (518.26,531.44).

Option (b) is correct.