Question

   A random sample of size 15 taken from a normally distributed population revealed a sample mean of 75 and a sample variance of 25. The upper limit of a 95% confidence interval for the population mean would equal:

Group of answer choices

72.727.

77.273.

77.769.

72.231.

Answer 1

here we do not have the population variance and the data is normally distributed so we can use the t-dist for the population mean interval.

(1- )% is the confidence interval for population mean

Where 75

n = 15

Sx = ....................where var = 25

Alpha =1 - 0.95 = 0.05

Therefore the C.V. =

=

= 2.14479 .............found using t-dist tables

Substituting the value

Where Margin of error = C.v. * SE

=

The upper limit =

The tail is not mentioned so we assume it is two tailed.