In: Statistics and Probability
Bob Nale would like to determine the mean number of gallons of gasoline sold to his customers. Assume the number gallons of gasoline sold is 2 gallons. From his records, he selects 64 samples and finds the mean is 9 gallons. Find the 95% confidence interval for the population mean.
point estimate , x̅ = 9
σ =2
n = 64
Level of Significance , α =
0.05
' ' '
z value= z α/2= 1.9600 [Excel
formula =NORMSINV(α/2) ]
Standard Error , SE = σ/√n = 2.000 /
√ 64 = 0.2500
margin of error, E=Z*SE = 1.9600
* 0.250 = 0.490
confidence interval is
Interval Lower Limit = x̅ - E = 9.00
- 0.490 = 8.5100
Interval Upper Limit = x̅ + E = 9.00
- 0.490 = 9.4900
95% confidence interval is (
8.51 < µ < 9.49
)