In: Statistics and Probability
In a manufacturing process a random sample of 36 bolts manufactured has a mean length of 3 inches with a standard deviation of .3 inches. What is the 99% confidence interval for the true mean length of the bolt?
Solution :
Given that,
= 3
= 0.3
n = 36
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
Margin of error = E = Z/2* ( /n)
= 2.576 * (0.3 / 36)
= 0.1288
At 99% confidence interval estimate of the population mean is,
- E < < + E
3 - 0.1288 < < 3 + 0.1288
2.8712< < 3.1288
(2.8712 , 3.1288 )