Question

Suppose the mean height in inches of all 9th grade students at one high school is estimated. The population standard deviation is 3 inches. The heights of 9 randomly selected students are 60, 61, 70, 65, 65, 60, 69, and 70.

x-bar =

Margin of error at 99% confidence level =

99% confidence interval =

Answer 1

Solution :

Given set of score are

60, 61, 70, 65, 65, 60, 69, and 70.

Mean = x / n

= 60+61+70+65+65+60+69+70 / 8

= 520 / 8 = 65

Mean = 65

Point estimate = sample mean = = 65

population standard deviation = = 3

sample size = n = 9

Z_/2 = 2.576

Margin of error = E = Z_/2* ( /n)

= 2.576 * (3 / 9)

Margin of error = E = 2.6

At 99% confidence interval estimate of the population mean is,

- E < < + E

65 - 2.6 < < 65 + 2.6

62.4 < < 67.6

99% confidence interval = 62.4 , 67.6