In: Statistics and Probability
Scenario 8.2
The undergraduate grade point average (GPA) for students admitted to the top graduate business schools was 3.37. Assume this estimate was based on a sample of 90 students admitted to the top schools. Using past years' data, the population standard deviation can be assumed known as 0.30.
1. Based on the information in Scenario 8.2, you are to
construct a 95% confidence interval estimate of the mean
undergraduate GPA for students admitted to the top graduate
business schools, that is
[ Lower limit , Upper limit ].
The Lower limit of this 95% confidence interval is equal to ? (to 2 decimals)?
2. Based on the information in Scenario 8.2, you are to
construct a 95% confidence interval estimate of the mean
undergraduate GPA for students admitted to the top graduate
business schools, that is
[ Lower limit , Upper limit ].
The Upper limit of this 95% confidence interval is equal to ? (to 2 decimals)?
The formula for confidence interval estimation is:
μ = M ± Z(sM)
where:
M = sample mean
Z = Z statistic determined by confidence
level
sM = standard error =
√(s2/n)
M = 3.37
Z = 1.96
sM = √(0.32/90) =
0.03
μ = M ± Z(sM)
μ = 3.37 ± 1.96*0.03
μ = 3.37 ± 0.062
95% CI [3.308, 3.432].
The lower limit is 3.31
2. The Upper limit is 3.43
Z table used for Z value calculation at 95% confidence level is