In: Statistics and Probability
A study of 35 apple trees showed that the average number of apples per tree was 725. The standard deviation of the population is 100. Which of the following is the 99% confidence interval for the mean number of apples per tree for all trees?
Solution :
Given that,
Point estimate = sample mean =
= 725
Population standard deviation =
= 100
Sample size = n =35
At 99% confidence level the z is ,
= 1 - 99% = 1 - 0.99 = 0.01
/ 2 = 0.01 / 2 = 0.005
Z/2 = Z0.005 = 2.576 ( Using z table )
Margin of error = E = Z/2* ( /n)
=2.576 * (100 / 35)
= 43.5423
At 99% confidence interval estimate of the population mean is,
- E < < + E
725-43.5423 < < 725+43.5423
681.4577< < 768.5423
( 681.4577, 768.5423)