Question

17. In a random sample of 30 business students, the average time to complete a statistics exam was 43.4 minutes. Assume that the population standard deviation to complete the exam is 8.7 minutes. The margin of error for an 80% confidence interval around this sample mean is ________.

Answer 1

Solution :

Given that,

Point estimate = sample mean =     = 43.4

Population standard deviation =    =  8.7

Sample size n =30

At 80% confidence level the z is ,

= 1 - 80% = 1 - 0.80 = 0.20

/ 2 = 0.10

Z/2 = Z0.10 = 1.28 ( Using z table )

Margin of error = E =   Z/2    * ( /n)
= 1.28 * (  8.7 / 30 )

E= 2.0331

Margin of error = E = 2.0331