It is well documented that active maternal smoking during pregnancy is associated with​ lower-birth-weight babies. Researchers 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 accompanying data are representative of 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. Complete parts​ (a) through​ (g) below.
a.) It is____________ (a designed experiment OR an observational study) because the researchers ____________(intentionally changed OR the value of an explanatory variable.
b.) What is the explanatory​ variable? What is the response​ variable?
Explanatory variable is ___________(whether or not the mothers smoked OR smokers OR whether or not the father smoked OR non smokers OR birth weight.)
Response variable is__________ (whether or not the mothers smoked OR smokers OR whether or not the father smoked OR non smokers OR birth weight.)
c.) Can you think of any lurking variables that may affect the results of the​ study? Select all that apply.
-Shopping habits
-Eating habits
-​Father's weight
-Exercise habits
-Whether the mother received prenatal care
​d.) In the​ article, the researchers stated that​ "birthweights were adjusted for possible​confounders..." What does this​ mean?
-The researchers attempted to adjust their results for any variables that may also be related to smokers.
-The researchers attempted to adjust their results for any variables that may also be related to nonsmokers.
-The researchers attempted to adjust their results for any variables that may also be related to birth weight.
-The researchers attempted to adjust their results for any variables that may also be related to​ father's weight.
e.) Determine the summary statistics.
Nonsmokers mean=___ grams
Nonsmokers median=____ grams
Nonsmokers standard deviation= ____ grams
Nonsmokers first quartile=_____ grams
Nonsmokers third quartile=____ grams
Smokers mean=___ grams
Smokers median=____ grams
Smokers standard deviation= ____ grams
Smokers first quartile=_____ grams
Smokers third quartile=____ grams
​f.) Interpret the first quartile for both the nonsmoker and smoker group.
OPTION A. For the two​ groups, 50% of infants in each group have birth weights less than or equal to the first quartile for that​group, and​ 50% of infants in each group have birth weights greater than the first quartile for that group.
OPTION B.For the two​ groups, 25% of infants in each group have birth weights less than or equal to the first quartile for that​group, and​ 75% of infants in each group have birth weights greater than the first quartile for that group.
OPTION C.For the two​ groups, 75% of infants in each group have birth weights less than or equal to the first quartile for that​group, and​ 25% of infants in each group have birth weights greater than the first quartile for that group.
g.) Draw a​ side-by-side boxplot of the data. Does the​ side-by-side boxplot confirm the conclusions of the​ study?
Does the​ side-by-side boxplot confirm the conclusions of the​study?
OPTION A.The boxplot does not confirm the study as the medians are very close to each​ other; the third quartiles are noticeably​different, but not the medians.
OPTION B.The boxplot does not confirm the study as the median for smokers is significantly more than the median for​ nonsmokers; the median is located close to the third quartile of nonsmokers.
OPTION C. The boxplot confirms the study as the median for smokers is significantly more than the median for​ nonsmokers; the median is located close to the third quartile of nonsmokers.
OPTION D. The boxplot confirms the study as the median for smokers is significantly less than the median for​ nonsmokers; the median is located close to the first quartile