It is welldocumented that parents actively smoking during pr

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.

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?

D.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.

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

F.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

Solution

a)

This is a designed experiment as one is trying influence results by changing the factors such as smoking habits

b)

explanatory variable is smoking habit as it is independent

response variable is birth weight of babies

c)
lurking variable is one which influences both the factors

one such example is the weight of parent

d)

Non-smokers:

Sample Size:       27
Mean:       3648.481481
Geometric Mean:       3630.941171
Minimum:       2976
Maximum:       4354
         
1st Quartile:       3429.5
Median:       3668
3rd Quartile:       3899.5
Interquartile Range:       470
Range:       1378

smokers:

Sample Size:       27
Mean:       3475.185185
Geometric Mean:       3443.837772
Minimum:       2746
Maximum:       4263
         
1st Quartile:       3097.5
Median:       3502
3rd Quartile:       3849.5
Interquartile Range:       752
Range:       1517

E)

sample standard deviation only finds deviation for current sample where as population standard deviation estimates deviation based on sample , hence the different values

sample standard deviation is used in this study as we donot have entire population data

F)Yes, the data shows that the birth weight babies of fathers who smoke is less than the birth weight babies of fathers who donot smoke