Question

A. How many samples do you need to create a 99% confidence interval for u with a margin of error fo 10 and standard deviation of 28?

B. Five a 95% percent confidence interval for the true mean if the sample mean is 86.5, the sample size is 70, and the standard deviation is 12.2.

Answer 1

Solution :

Given that,

=86.5

= 12.2

n = 70

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z_/2 = Z_0.025 = 1.96

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

= 1.96 * (12.2 / 70)

= 2.8580

At 95% confidence interval estimate of the population mean is,

- E < < + E

86.5 - 2.8580 < < 86.5 +2.8580

83.6420< < 89.3580

(83.6420 , 89.3580 )