In: Statistics and Probability
Use the given data to find the 95% confidence interval estimate of the population mean μ. Assume that the population has a normal distribution.
IQ scores of professional athletes:
Sample size n=20
Mean x¯¯¯=104
Standard deviation s=14
<μ<
Solution :
Given that,
= 104
s =14
n = Degrees of freedom = df = n - 1 = 20- 1 = 19
At 95% confidence level the t is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2= 0.05 / 2 = 0.025
t /2,df = t0.025,19 = 2.093 ( using student t table)
Margin of error = E = t/2,df * (s /n)
= 2.093* ( 14/ 20)
= 6.55
The 95% confidence interval mean is,
- E < < + E
104 - 6.55 < < 104+ 6.55
97.45 < < 110.55