In: Math
Mean=33,820.21
Standard Deviation=22,948.45
n=52
Calculate a 99% confidence interval, assuming that sigma is unknown.
Level of Significance , α =
0.01
degree of freedom= DF=n-1= 51
't value=' tα/2= 2.6757 [Excel
formula =t.inv(α/2,df) ]
Standard Error , SE = s/√n = 22948.4500 /
√ 52 = 3182.3774
margin of error , E=t*SE = 2.6757
* 3182.3774 = 8515.1580
confidence interval is
Interval Lower Limit = x̅ - E = 33820.21
- 8515.158045 =
25305.0520
Interval Upper Limit = x̅ + E = 33820.21
- 8515.158045 =
42335.3680
99% confidence interval is (
25305.05 < µ < 42335.37
)