In: Statistics and Probability
If X=66, S=27 and n=36, and assuming that the population is normally distributed, construct a 95 % confidence interval estimate of the population mean.
Solution :
Given that,
= 66
s =27
n =36
Degrees of freedom = df = n - 1 =36 - 1 = 35
At 95% confidence level the t is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2= 0.05 / 2 = 0.025
t /2,df = t0.025,35 = 2.030 ( using student t table)
Margin of error = E = t/2,df * (s /n)
= 2.030 * (27 / 36)
= 9.1
The 95% confidence interval estimate of the population mean is,
- E < < + E
66-9.1 < < 66+ 9.1
56.9 < < 75.1