Question

**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:**

- (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.*

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