In: Statistics and Probability
A random sample of 110 light bulbs had a mean line of x̅=595 hours. Assume that σ=31 hours. Construct 90% confidence interval for the mean life μ, of all light bulbs of this type
z0.1 1.282
z0.05 1.645
z0.025 1.960
z0.01 2.326
z0.005 2.576
Given that,
= 595
= 31
n = 110
At 90% confidence level the z is ,
= 1 - 90% = 1 - 0.90 = 0.10
/ 2 = 0.10 / 2 = 0.05
Z/2 = Z0.05 = 1.645
Margin of error = E = Z/2* ( /n)
= 1.645* (31 / 110)
= 4.8622
At 90% confidence interval estimate of the population mean is,
- E < < + E
595 - 4.8622 < < 595 + 4.8622
590.1378< < 599.8622
(590.1378 , 599.8622 )