In: Statistics and Probability
A sample of 73 oversized packages delivered by OOPS (Only Oversized Parcel Service) is randomly selected and weighed, producing an average weight of 61.3 lbs. Assuming that the population standard deviation is known to be 9.2 lbs, find a 95% confidence interval estimate for the average weight of all oversized packages delivered by OOPS.
Solution
Given that,
=61.3
= 9.2
n = 73
A ) At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.960
Margin of error = E = Z/2* (/n)
= 1.960 * (9.2 / 73)
= 2.11
At 95% confidence interval estimate of the population mean is,
- E < < + E
61.3 - 2.11 < < 61.3 + 2.11
59.19 < < 63.41
(59.19 , 63.41)