Question

a published wants to estimate the mean length of time all adults spend reading news papers. to determine the estimate the publisher take a random number sample of 15 people and obtained the results below. from past studies, the publisher assumes õ is 1.7 minutes and that the population of times normally distributed.
6, 10,10,11,11,10,6,8,7,7,8,7,8,12,9.
construct the 90% and 99% confidence intervals for the population mean,

Answer 1

Answer

it is given that sample size is n =15 and population standard deviation = 1.7

Mean = (sum of all observations)/(total number of observations)

= (6+10+10+11+11+10+6+8+7+7+8+7+8+12+9)/15

90% confidence interval calculation

z score for 90% confidence interval is z = 1.645 (using z table)

Confidence interval =

99% confidence interval calculation

z score for 99% confidence interval is z = 2.58 (using z table)

Confidence interval =