Stat 401B
Lab 2
Due September 12, 2006
1
Last week’s lab looked at the data on forced expiratory volume (FEV). The data are available
on the course Web site:
www.public.iastate.edu/∼wrstephe/stat401.html
Use JMP to analyze the residuals for the two problems below. It is not sufficient
to simply hand in JMP output. You must answer the questions completely. Hand
in the JMP output attached at the end of your written solutions.
1. One-sample problem.
(a) Use JMP to create residuals for the 100 FEV measurements.
(b) Refer to the histogram of residuals and indicate what you see and what this tells
you about the condition that the random errors are normally distributed.
(c) Refer to the box plot of residuals. Are there any possible outliers? If so, what are
these FEV values and the corresponding sex, height and age of the individuals.
What does this tell you about the condition of identically distributed random
errors?
(d) Refer to the Normal Quantile Plot of residuals and indicate what you see and
what this tells you about the condition that the random errors come from a
normal distribution.
(e) Summarize what you have learned about the conditions necessary for the statistical analysis of the FEV data from your analysis of the residuals.
2. Two-sample problem.
(a) Use JMP to create the residuals for the two sets, male and female, of 50 FEV
measurements.
(b) Refer to the histogram of residuals and indicate what you see and what this tells
you about the condition that the random errors are normally distributed.
(c) Refer to the box plot of residuals. Are there any possible outliers? If so, what are
these FEV values and the corresponding sex, height and age of the individuals.
What does this tell you about the random errors being identically distributed?
(d) Refer to the Normal Quantile Plot of residuals and indicate what you see and what
this tells you about the condition that the random errors are normally distributed?
(e) Comment on the whether or not the data are consistent with the condition that
both populations (male and female) have the same standard deviation.
(f) Summarize what you have learned about the conditions necessary for statistical
analysis of data from your analysis of residuals.
3. Comment on what effect, if any, that your findings in problems 1 and 2 have on the
inferences made using these data.