Main Class Discussion

Nonsmokers
4194 3522
3454 3062 3771 3783 3544 3746 4019 4248 3719 3668 3128 3290 3423 3471 4354 3544 3994 2976 4067 3732 3823 3302 3436 3976 3263

Smokers
3998	3455	3066
3150	2986	2918
4216	3502	3457
2860	3282	2746
3686	2851	3145
3807	3548	4104
3963	3892	2768
3769	3509	3629
4131	3129	4263

1. Is this an observational study or a designed experiment? Why?
2. What is the explanatory variable? What is the response variable?
3. Can you think of any lurking variables that may affect the results of the study?
4. Go to http://www.xuru.org/st/DS.asp and find the summary statistics for both non-smokers and smokers (mean, median, standard deviation, quartiles.) Compute each group separately. Report your findings. Note: Copy the data from the tables and place in the large box on the page and separate each item by a comma.
5. Why is the sample standard different from the population standard deviation? Which should you use in this study, and why?
6. Using your results, write up a practical summary of what you are seeing in this data. Do you agree with the researchers’ conclusions based on your analysis?