Chapter 8 Homework
December 8, 2012
1. Problem Definition: Compute a 95% confidence interval for the mean the diameter of holes drilled in a steel plate.
One-Sample Z
The assumed standard deviation = 0.005
N Mean SE Mean 95% CI
15 2.47500 0.00129 (2.47247, 2.47753)
Conclusion: We are 95% confident that the true population parameter lies within the interval (2.47247, 2.47753).
Interpretation: We are 95% confident the population mean the diameter of holes in a steel plate will be between (2.47247, 2.47753) cm. The interval estimate will be incorrect 5% of the time meaning the population parameter will not be contained within the interval.
2. Problem Definition: Compute a 90% confidence interval to estimate μ.
One-Sample T: Waiting time
Variable N Mean StDev SE Mean 90% CI
Waiting time 16 19.875 3.649 0.912 (18.276, 21.474)
Boxplot of Waiting time
Satisfying the normality assumption: The mean and median lie within the mid-spread and the variability on either side of the mid-spread is nearly equal as show by the similar lengths of the whisker lines. These characteristics will become more prevalent as the sample size increases.
Conclusion: We are 90% confident that the pharmacy customers waiting time lies within the interval (18.276, 21.474).
Interpretation: We are 90% confident the mean waiting time will between (18.276, 21.474). The interval estimate will be incorrect 10% of the time meaning the pharmacy customers