Question

We want to estimate the population mean within 4, with a 80% level of confidence. The population standard deviation is estimated to be 9. How large a sample is required? (Round the intermediate calculation to 2 decimal places. Round the final answer to the nearest whole number.) Sample size

Answer 1

Solution :

Given that,

standard deviation = = 9

margin of error = E = 4

At 80% confidence level the z is ,

= 1 - 80% = 1 - 0.80 = 0.20

/ 2 = 0.20 / 2 = 0.10

Z/2 = Z 0.10 = 1.28

Sample size = n = ((Z/2 * ) / E)2

= ((1.28 * 9 ) / 4 )2

= 8

Sample size = 8