In: Statistics and Probability
A random sample of 45 life insurance policy holders showed that the average premiums paid on their life insurance policies was $345 per year with a sample standard deviation of $65.
Solution :
Given that,
= $345
s = $65
n = 45
Degrees of freedom = df = n - 1 = 45 - 1 = 44
)At 90% confidence level the t is ,
= 1 - 90% = 1 - 0.90 = 0.1
/ 2 = 0.1 / 2 = 0.05
t /2,df = t0.05,44=1.680
Margin of error = E = t/2,df * (s /n)
= 1.680 * (65/ 45) = 16.2786
The 90% confidence interval estimate of the population mean is,
- E < < + E
345 - 16.2786 < < 345+ 16.2786
328.7214 < < 361.2786
(328.7214, 361.2786)