Statistics

It is well-documented that parents' actively smoking during pregnancy is associated with lower-birth-weight babies. Researchers Fernando D. Martinez and associates wanted to determine if there is a relationship between paternal smoking habits and birth weight. The researchers administered a questionnaire to each parent of newborn infants. One question asked whether the individual smoked regularly. Because the survey was administered within 15 days of birth, it was assumed that any regular smokers were also regular smokers during pregnancy. Birth weights for the babies (in grams) of nonsmoking mothers were obtained and divided into two groups, nonsmoking fathers and smoking fathers. The given data below represents the data collected by the researchers. The researchers concluded that the birth weight of babies whose father smoked was less than the birth weight of babies whose father did not smoke.

Answer the following questions for your main post:
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

a. Is this an observational study or a designed experiment? Why?

b. What is the explanatory variable? What is the response variable?

c. Can you think of any lurking variables that may affect the results of the study?
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.

d. Why is the sample standard different from the population standard deviation? Which should you use in this study, and why?

e. 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?