Statistics
Renal Disease The mean serum-creatinine level measured in 12 patients 24 hours after they received a newly proposed antibiotic was 1.2 mg/dL.
1. If the mean and standard deviation of serum creatinine in the general population are 1.0 and 0.4 mg/dL, respectively, then, using a significance level of .1, test whether the mean serum-creatinine level in this group is different from that of the general population.
2. What is the p-value for the test?
3. Suppose the sample standard deviation of serum creatinine in Problem 1 is 0.7 mg/dL. Assume that the standard deviation of serum creatinine is not known, and perform the hypothesis test in Problem 1. Report a p- value.
4. Compute a two-sided 95% CI for the true mean serum-creatinine level in Problem 3.
Endocrinology Refer to Data Set BONEDEN.DAT at www.cengagebrain.com.
5. Perform a hypothesis test (with significance level α = 0.1) to assess whether there are significant differences in mean BMD for the femoral neck between the heavier- and lighter-smoking twins.
6. Answer Problem 5 for mean BMD at the femoral shaft.
Environmental Health, Pulmonary Disease A
clinical epidemiologic study was conducted to determine the long-term health effects of workplace exposure to the process of manufacturing the herbicide (2,4,5 trichlorophenoxy) acetic acid (2,4,5-T), which contains the contaminant dioxin. This study was conducted among active and retired workers of a Nitro, West Virginia, plant who were exposed to the 2,4,5-T process between 1948 and 1969. It is well known that workers exposed to 2,4,5-T have high rates of chloracne (a generalized acneiform eruption). Less well known are other potential effects of 2,4,5-T exposure. One of the variables studied was pulmonary function. Suppose the researchers expect from general population estimates that 4% of workers have an abnormal forced expiratory volume (FEV); defined as less than 80% of predicted, based on their age and height. They found that 32 of 203 men who were exposed to 2,4,5-T while working at the plant had an abnormal FEV.
7. What hypothesis test can be used to test the hypothesis that the percentage of abnormal FEV values among exposed men differs from the general-population estimates?
8. Implement the test in Problem 7, and report a p-value (two-tailed). Another type of outcome reported was fetal deaths. Suppose the investigators expect, given general population pregnancy statistics at the time of the survey, that 1.5% of pregnancies will result in a fetal death. They found that among 586 pregnancies where an exposed worker was the father, 11 resulted in a fetal death.
9. Provide a 95% CI for the underlying fetal death rate among offspring of exposed men. Given the CI, how do you interpret the results of the study?