In: Statistics and Probability
A laboratory tested twelve chicken eggs and found that the mean amount of cholesterol was 230 milligrams with s = 11.3 milligrams. Construct a 95% confidence interval for the true mean cholesterol content of all such eggs.
Solution :
Given that,
= 230
s = 11.3
n = 12
Degrees of freedom = df = n - 1 = 12 - 1 = 11
At 95% confidence level the t is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
t /2,df = t0.025,11 =2.201
Margin of error = E = t/2,df * (s /n)
= 2.201 * (11.3 / 12)
= 7.18
Margin of error = 7.18
The 95% confidence interval estimate of the population mean is,
- E < < + E
230 - 7.18 < < 230 + 7.18
222.82 < < 237.18
(222.82, 237.18 )