Questions and Answers of Fundamentals of Biostatistics

Fit a linear-regression model relating annual incidence of diabetes to time period. (For this purpose, score the time period as 1 if 1970ˆ’1974, 2 if 1975ˆ’1979, . . . , 5 if
If a serum-lutein value <5.0 μg/dL indicates that a participant is not taking lutein capsules, then what percentage of the placebo group is complying (not taking lutein capsules outside the
If a serum-lutein value >5.0 μg/dL indicates that a participant is taking lutein capsules, then what percentage of the active group is complying? (Assume the old assay is correct and that the
Suppose a participant had a 1999 serum-lutein level of 5.0 Î¼g/dL. What is that person€™s predicted serum lutein based on the 2003 assay? What is a 95% confidence interval
Using regression methods, derive a calibration formula predicting the 2003 level as a function of the 1999 level?OphthalmologyLutein, an important carotenoid in the maintenance of ocular health, has
Assess whether there is a significant relationship between bone density of the lumbar spine and bone density of the femoral neck. Please provide a two-tailed p-value?Table 11.25: Change in bone
Provide a 95% CI corresponding to the measure of association obtained in problem 11.82?Table 11.25: Change in bone density, femoral neck, over time Bone density, femoral neck (g/cm®) (y) Time
Provide a measure of association between bone density of the lumbar spine and bone density of the femoral neck?Table 11.25: Change in bone density, femoral neck, over time Bone density, femoral
The normal change in bone density over time from age 40 to age 80 is a decrease of 0.15 g/cm2. Does the rate of change in this woman differ significantly from the expected age-related
Provide a significance test to assess whether the mean bone density has changed significantly over time. Provide a two-tailed p-value?EndocrinologyA 65-year-old woman with low bone density in 2002
What is the estimated rate of increase in bone density of the lumbar spine per year? What is the standard error of the estimated rate of increase per year? EndocrinologyA 65-year-old woman with
Suppose we have an estimated rank correlation of .75 based on a sample of size 8. Assess the significance of the results?
Suppose we have an estimated rank correlation of .45 based on a sample of size 24. Assess the significance of the results?
Do you think parametric or non-parametric methods are better suited to analyze the data in VALID.DAT? Explain.
1. Use rank-correlation methods to relate alcohol intake as reported on the diet record with alcohol intake as reported on the food-frequency questionnaire?2. Answer Problem 11.72 for total fat
Consider other possible confounding variables in comparing the heavier- vs. lighter smoking twin. Repeat the analyses in Problems 11.67−11.70, adjusting for these confounding variables. What is
Answer the question in Problem 11.68 for bone density at the femoral neck?One of the issues in relating bone density to smoking is that smokers and nonsmokers differ in many other characteristics
Repeat the analyses in Problem 11.64 controlling for weight differences between the heavier- and the lighter smoking twins?One of the issues in relating bone density to smoking is that smokers and
Compare the weight of the heavier- vs. the lighter smoking twin using hypothesis-testing methods?One of the issues in relating bone density to smoking is that smokers and nonsmokers differ in many
Answer the question in Problem 11.64 for bone density at the femoral shaft?Data From 11.64Use regression analysis to relate the number of pack-years smoked to the bone density of the lumbar spine.
Answer the question in Problem 11.64 for bone density at the femoral neck?Data from 11.64Use regression analysis to relate the number of pack-years smoked to the bone density of the lumbar spine.
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?
Implement the method in Problem 11.61, and report a two-tailed p-value?HypertensionEndothelin is a powerful vasoconstrictor peptide derived from the endothelium. The contribution of endothelin to
What test can be used to assess whether the mean change in SBP is significantly related to ln(dose) of Bosentan?HypertensionEndothelin is a powerful vasoconstrictor peptide derived from the
Fit a regression line relating the mean change in SBP to the ln(dose) of Bosentan. (Note: For the placebo group, assume the dose of Bosentan = 1 mg; hence the ln(dose) =
Provide a 95% Cl for the estimate in Problem 11.58?Cardiovascular DiseaseThe STRIP study (Special Turku Coronary Risk Factor Intervention Project for Children) is a longitudinal randomized prevention
What is the expected HDL-C for an average person with a waist circumference= 90 cm?Cardiovascular DiseaseThe STRIP study (Special Turku Coronary Risk Factor Intervention Project for Children) is a
Determine the slope and intercept of the least squares regression line of HDL-C on waist circumference, and write out the equation of the least squares regression line?Cardiovascular DiseaseThe STRIP
Provide a 95% confidence interval for the correlation coefficient.The mean ± sd for waist circumference was 72.8 ± 7.8 cm.The mean ± sd for HDL-C was 20.7 ± 4.1 mg/dl. Cardiovascular
Perform the test in Problem 11.54, report a twotailed p-value, and state your conclusion clearly, in context?Cardiovascular DiseaseThe STRIP study (Special Turku Coronary Risk Factor Intervention
Suppose we wish to perform a test to assess whether the correlation coefficient is significantly different from 0. State the hypotheses to be tested, the algebraic form of the test statistic used to
Suppose we wanted to use data on children of all gestational ages in the study. Suggest a type of analysis that could be used to relate the Bayley score to severe hypothyroxinemia while controlling
Perform a test to compare the mean Bayley score between children with and without severe hypothyroxinemia (report a p-value)?To test the primary hypothesis of the study, infants were categorized by
Assess the goodness of fit of the regression line fitted in Problem 11.49?Pediatrics, EndocrinologyTransient hypothyroxinemia, a common finding in premature infants, is not thought to have long-term
Is there a significant association between mean thyroxine level and gestational age? Report a p-value. Pediatrics, EndocrinologyTransient hypothyroxinemia, a common finding in premature infants,
Use regression methods to look at the relationship between level of pulmonary function and other factors (e.g., age, height, and personal smoking) when considered separately and simultaneously.
Use methods of linear-regression analysis to assess whether there are dose−response relationships with regard to biliary and pancreatic secretion levels. Perform separate analyses for each of the
Use methods of linear-regression analysis to assess whether there are dose–response relationships with regard to biliary and pancreatic pH levels. Perform separate analyses for each of the four
What test can be used to assess whether there is a significant association between LDL cholesterol and ponderal index? Pediatrics, Cardiovascular DiseaseAn important area of investigation is the
Implement the test in Problem 11.39 for Caucasian boys, and report a two-sided p-value?Pediatrics, Cardiovascular DiseaseAn important area of investigation is the development of strategies for
What test can be used to compare correlations between Caucasian and African American boys?Pediatrics, Cardiovascular DiseaseAn important area of investigation is the development of strategies for
Implement the test in Problem 11.41, and report a p-value?Pediatrics, Cardiovascular DiseaseAn important area of investigation is the development of strategies for altering cardiovascular risk
Provide a 95% confidence interval for the true correlation among Caucasian boys (ρ1) and African American boys (ρ2), respectively?Pediatrics, Cardiovascular DiseaseAn important area of
Use linear-regression methods to relate each salt and sugar index proposed to systolic blood pressure (SBP). Assess the goodness of fit of the proposed models; use appropriate data transformations,
Answer Problem 11.44 for diastolic blood pressure?Data from 11.44Use linear-regression methods to relate each salt and sugar index proposed to systolic blood pressure (SBP). Assess the goodness of
Use regression methods to assess the relationship between full-scale IQ (IQF) and lead exposure group, where lead exposure is quantified as a categorical variable with two categories (exposed and
LD72 and LD73 are variable names for the actual blood-lead levels in 1972 and 1973, respectively. Use regression methods to assess the relationship between MAXFWT and the actual blood-lead level(s),
Answer the same questions posed in Problem 11.47 for IQF?Data from 11.47LD72 and LD73 are variable names for the actual blood-lead levels in 1972 and 1973, respectively. Use regression methods to
What is the best-fitting regression line relating mean thyroxine level to gestational age?Pediatrics, EndocrinologyTransient hypothyroxinemia, a common finding in premature infants, is not thought to
Provide 95% confidence limits for each of your estimates?
Assess the agreement between the food-frequency questionnaire and the dietary record with regard to total fat intake, saturated fat intake, alcohol intake, and total caloric intake. Quantify the
Provide a 95% confidence interval for the correlation coefficient between these two measures of reactivity?HypertensionRefer to the data in Table 3.11 (on p. 69). Another method for relating measures
Conduct the test procedure in Problem 11.31, and report a p-value. What do the results mean, in words?HypertensionRefer to the data in Table 3.11 (on p. 69). Another method for relating measures of
What is the appropriate procedure to test if there is a relationship between reactivity as measured by the automated and manual monitors? HypertensionRefer to the data in Table 3.11 (on p. 69).
Provide a two-sided p-value and a 95% Cl associated with this coefficient?HypertensionThe INTERSALT Study investigators collected standardized data on timed 24-hour urinary excretion for 10,079 men
What does the regression coefficient for casual potassium (-0.13) mean in words?HypertensionThe INTERSALT Study investigators collected standardized data on timed 24-hour urinary excretion for 10,079
Provide a 95% Cl for the true slope (β)?HypertensionThe INTERSALT Study investigators collected standardized data on timed 24-hour urinary excretion for 10,079 men and women from 52 population
What is the estimated standard error of the slope estimate?HypertensionThe INTERSALT Study investigators collected standardized data on timed 24-hour urinary excretion for 10,079 men and women from
What does the R2 of 0.27 mean in words? HypertensionThe INTERSALT Study investigators collected standardized data on timed 24-hour urinary excretion for 10,079 men and women from 52 population
What does the R2 of 0.27 mean in words? HypertensionThe INTERSALT Study investigators collected standardized data on timed 24-hour urinary excretion for 10,079 men and women from 52 population
Why are the variables mortality rate and annual cigarette consumption expressed in the log10scale?CancerThe following statistics are taken from an article by Burch relating cigarette smoking to lung
What is the expected lung-cancer mortality rate with an annual cigarette consumption of 1 lb/person?CancerThe following statistics are taken from an article by Burch relating cigarette smoking to
To test the significance of this regression line, is it necessary to perform any additional tests other than those in Problem 11.20? If so, perform them.CancerThe following statistics are taken from
Fit a regression line relating 5-year lung-cancer mortality to annual cigarette consumption when each is expressed in the log10scale?CancerThe following statistics are taken from an article by Burch
Test this correlation for statistical significance, and report a p-value?CancerThe following statistics are taken from an article by Burch relating cigarette smoking to lung cancer [13]. The article
Compute the correlation between 5-year lungcancer mortality and annual cigarette consumption when each is expressed in the log10scale?CancerThe following statistics are taken from an article by Burch
Do you think the linear regression provides a good fit to the data? Why or why not? Use residual analysis to justify your answer.Table 11.18: 90th percentile of SBP in boys ages 1ˆ’17 of
Answer Problems 11.15 and 11.16 for a 17-year-old boy?Table 11.18: 90th percentile of SBP in boys ages 1ˆ’17 of average height
What is the standard error of the estimate in Problem 11.15? Table 11.18: 90th percentile of SBP in boys ages 1ˆ’17 of average height
What is the predicted blood pressure for an average 13-year-old boy as estimated from the regression line? Table 11.18: 90th percentile of SBP in boys ages 1ˆ’17 of average height
Provide a 95% confidence interval for the parameters of the regression line?Table 11.18: 90th percentile of SBP in boys ages 1ˆ’17 of average height
Fit a regression line relating age to SBP, using the data in Table 11.18?HypertensionThe Update to the Task Force Report on Blood Pressure Control in Children [12] reported the observed 90th
Test for whether the true correlation coefficients differ between these groups. Report a p-value?Suppose the correlation coefficient between weight is .78 for the 100 sets of identical twins and .50
What is the p-value of the test?Pulmonary FunctionSuppose the correlation coefficient between FEV for 100 sets of identical twins is .7, whereas the comparable correlation for 120 sets of fraternal
Perform the procedure in Problem 11.9 using the critical-value method?Pulmonary FunctionSuppose the correlation coefficient between FEV for 100 sets of identical twins is .7, whereas the comparable
What test procedure can be used to compare the two correlation coefficients? Pulmonary FunctionSuppose the correlation coefficient between FEV for 100 sets of identical twins is .7, whereas the
What is the z transformation of .34? HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17: Hematologic data for patients with aplastic anemia
What are the standard errors of the slope and intercept for the regression line in Problem 11.1? HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17:
Test for the statistical significance of the regression line using the t test?HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17: Hematologic data for
What is s2y.x? HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17: Hematologic data for patients with aplastic anemia
What does R2mean in Problem 11.3? HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17: Hematologic data for patients with aplastic anemia
What is R2for the regression line in Problem 11.1? HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17: Hematologic data for patients with aplastic
Test for the statistical significance of this regression line using the F test?HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17: Hematologic data for
Fit a regression line relating the percentage of reticulocytes (x) to the number of lymphocytes (y)?HematologyThe data in Table 11.17 are given for 9 patients with aplastic anemia [11].Table 11.17:
Compare your results in Problems 10.149 and 10.151. Which do you think is a better method of analysis? A more efficient method of analysis would leave the change in retinopathy level in its raw
Reanalyze the data in Table 10.49 using the Wilcoxon rank sum test?Table 10.49: Outcome data for the Sorbinil Retinopathy Trial (n = 481) change in retinopathy level A more efficient method of
Implement the test in Problem 10.149, and provide a p-value (two-tailed)?A more efficient method of analysis would leave the change in retinopathy level in its raw form without grouping the data but
What test can be used to compare the two groups if this more efficient method is used? A more efficient method of analysis would leave the change in retinopathy level in its raw form without
Implement the test in Problem 10.147, and provide a p-value (two-tailed)?OphthalmologyThe Sorbinil Retinopathy Trial was conducted among 497 type I (insulin-dependent) diabetic patients who had
What test can be used to compare the two treatment groups on the primary endpoint?OphthalmologyThe Sorbinil Retinopathy Trial was conducted among 497 type I (insulin-dependent) diabetic patients who
State the hypotheses to be tested under the null and alternative hypotheses?The results for the primary endpoint are given in Table 10.47.Table 10.47: Comparison of vascular outcomes by treatment
What test can be used to compare event rates among the three groups? The results for the primary endpoint are given in Table 10.47.Table 10.47: Comparison of vascular outcomes by treatment group
Implement the test in Problem 10.136, and report a p-value (two-tailed)?The results for the primary endpoint are given in Table 10.47.Table 10.47: Comparison of vascular outcomes by treatment group
What test can be performed to study the association between case/control status and risk score? Specifically, we are interested in testing whether cases tend to have consistently higher risk scores
Perform the test in Problem 10.139, and report a p-value (two-tailed)?OphthalmologyA caseˆ’control study was performed among 145 subjects with macular degeneration and 34 controls, all of
What is the estimated prevalence of AMD among women with a risk score in group 1? In group 6? Another use for the risk score is to compute a prevalence estimate of AMD for women with different
What is the relative risk for AMD among women in group 6 compared with women in group 1? What does the relative risk mean in words? Another use for the risk score is to compute a prevalence
How many subjects should be recruited in each group (same number per group) to have a 90% chance of detecting a significant difference using a two-sided test with α = .05?Pulmonary DiseaseAsthma is
Suppose that 50 households are randomized per group. How much power would the study have under the above assumptions?Pulmonary DiseaseAsthma is an important health problem for inner-city children,
What test can be used to compare the results in the active and control groups?The results of the study were as follows: 14 of the 50 active intervention children had an improvement in symptoms

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