population std dev , σ = 4.1000
Sample Size , n = 225
Sample Mean, x̅ = 14.3000
Level of Significance , α =
0.05
' ' '
z value= z α/2= 1.9600 [Excel
formula =NORMSINV(α/2) ]
Standard Error , SE = σ/√n = 4.100 /
√ 225 = 0.2733
margin of error, E=Z*SE = 1.9600
* 0.273 = 0.536
confidence interval is
Interval Lower Limit = x̅ - E = 14.30
- 0.536 = 13.7643
Interval Upper Limit = x̅ + E = 14.30
- 0.536 = 14.8357
95% confidence interval is (
13.76 < µ < 14.84
)
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