Refer to Data Set BONEDEN.DAT at www.cengagebrain .com.
3 Use regression analysis to relate the number of pack-years smoked to the bone density of the lumbar spine. Assess the goodness of fit of the regression line. (Hint: For a twinship, relate the difference in bone density between the heavier- and lighter-smoking twin to the difference in the number of pack-years of smoking.)
4 Answer the question in Problem 3 for bone density at the femoral neck.
5 Answer the question in Problem 3 for bone density at the femoral shaft. One of the issues in relating bone density to smoking is that smokers and nonsmokers differ in many other characteristics that may be related to bone density; these differences are referred to as confounders.
6 Compare the weight of the heavier- vs. the lightersmoking twin using hypothesis-testing methods.
7 Repeat the analyses in Problem 3 controlling for weight differences between the heavier- and the lightersmoking twins.
8 Answer the question in Problem 7 for bone density at the femoral neck.
9 Answer the question in Problem 7 for bone density at the femoral shaft.
Obesity is very common in American society and is a risk factor for breast cancer in postmenopausal women. One mechanism explaining why obesity is a risk factor is that it may raise estrogen levels in women. In particular, one biomarker of estrogen, serum estradiol, is a strong risk factor for breast cancer. To better assess these relationships, researchers studied a group of 151 African American and 60 Caucasian premenopausal women. Adiposity was quantified by two different measures: BMI = weight (kg)/height2 (m2) and waisthip ratio (WHR) = waist circumference/hip circumference. BMI is a measure of overall adiposity, whereas WHR is a measure of abdominal adiposity. In addition, a complete hormonal profile was obtained, including serum estradiol (ES_1). Finally, other breast-cancer risk factors were also assessed among these women, including (1) ethnicity (ETHNIC = 1 if African American, = 0 if Caucasian), (2) age (ENTAGE), (3) parity (NUMCHILD = number of children), (4) age at first birth (AGEFBO), (5) any children (ANYKIDS = 1 if yes, = 0 if no), (6) age at menarche (AGEMNRCH = age when menstrual periods began). The data are provided in Data Set ESTRADL. DAT at www.cengagebrain.com
10 Is there a crude association between either measure of adiposity (BMI, WHR), considered separately, and serum estradiol?
11 Are these relationships similar for Caucasian and African American women?
12 Do the relationships between the adiposity measures and serum estradiol persist after controlling for the other breast-cancer risk factors in list items 1 to 6?
13 It is well known that African American women have higher levels of obesity than Caucasian women. Are there differences between estradiol levels for African American women and Caucasian women after controlling for obesity?
14 Is there evidence of nonlinearity for age or for height?
15 What is the estimated mean FEV for a nonsmoking 15-year-old boy with height = 5’6” (66 inches)?