Questions and Answers of Fundamentals of Biostatistics

Is there a difference in incidence according to duration of use (Variables 14 and 15)?CancerThe data set in file BREAST.DAT consists of 1200 women in the NHS. The women were ascertained in 1990 and
Answer the question posed in Problem 14.69, while accounting for possible age and gender differences between groups?FIELD.DOCColumn _________________________________________ Variable1−6
Assess whether the time to legal blindness is the same or different between the RHO group and the RPGR group. For simplicity, assume that legal blindness in a particular eye is an absorbing state
It was found that among 626 Australian H1N1 patients admitted to an intensive care unit (ICU), 61 were aboriginal. If 2.5% of Australians are aboriginal, test the hypothesis that the percentage of
For each region,(i) Estimate the incidence rate per million (106) inhabitants (per week) over the 7-week period, and(ii) The number of cases over 7 weeks from 06/29/09 to 08/16/09 (rounded to the
Using the incidence rates calculated in Problem 14.73, test whether there are significant differences in incidence rates by region over the 7-week period. Provide a two-sided p-value. (Note: Assume
There were 722 patients admitted to the ICU for H1N1 in Australia and New Zealand from June 1 to August 31, 2009 (winter season). The total population of Australia and New Zealand is approximately
Estimate the incidence rate ratio (IRR) comparing mortality incidence between period A and period B, and provide a 95% CI about this estimate?CancerA study was conducted concerning the effect of
Estimate the incidence rate difference (IRD) comparing mortality incidence between period A and period B, and provide a 95% CI about this estimate?CancerA study was conducted concerning the effect of
Test the hypothesis that the IRR comparing period A to period B is the same as from period C to period D?One issue is that there may be time trends in breast cancer mortality that have nothing to do
Interpret what the results mean. Specifically, did the screening program have a significant impact on breast cancer mortality or not? One issue is that there may be time trends in breast cancer
What test can be performed to compare the breast cancer incidence rate between the ‰¥ 30.0g group and the 0g group? CancerA paper was recently published concerning the association
Perform the test in Problem 14.80, and report a p-value (two-tail)?CancerA paper was recently published concerning the association between alcohol consumption and breast cancer incidence based on
What is the estimated incidence rate ratio comparing the ‰¥30.0g group vs. the 0g group?CancerA paper was recently published concerning the association between alcohol consumption and breast
Provide a 95% CI for the IRR in Problem 14.82?CancerA paper was recently published concerning the association between alcohol consumption and breast cancer incidence based on Nurses€™
Perform a test for trend based on the data in Table 14.41?CancerA paper was recently published concerning the association between alcohol consumption and breast cancer incidence based on
Assess whether the rate of decline differs between RHO and RPGR patients?OpththalmologyRetinitis pigmentosa (RP) is a hereditary ocular disease in which patches of pigment appear on the retina; the
Assess whether the baseline level of visual field differs between RHO and RPGR patients?OpththalmologyRetinitis pigmentosa (RP) is a hereditary ocular disease in which patches of pigment appear on
Are there any interaction effects between PMH exposure and other risk factors?CancerThe data set in file BREAST.DAT consists of 1200 women in the NHS. The women were ascertained in 1990 and were
Perform an adjusted analysis comparing breast cancer incidence between the current PMH users vs. the never PMH users, adjusting for confounders that you found in Problem 14.65?CancerThe data set in
Compare the current PMH users vs. the never users in 1990 on other possible confounding variables?CancerThe data set in file BREAST.DAT consists of 1200 women in the NHS. The women were ascertained
Compare breast cancer incidence between the two exposure groups, where group 3 is the current PMH subjects and group 2 is the never PMH subjects?CancerThe data set in file BREAST.DAT consists of 1200
Suppose we want to enroll n subjects per group in the previously proposed study and follow each woman for 5 years. How many subjects do we need to achieve 90% power?Most risk factors seem of
Suppose we wish to conduct a clinical trial to study the association between ASA and colon cancer. We will enroll 50,000 women in the study, half of whom will be assigned to ASA and half to placebo.
Test the hypothesis that the hazard ratio for smoking ≥20 pack-years vs. never smoking is significantly different (at the 5% level) for men vs. women?Most risk factors seem of comparable magnitude
Test the hypothesis that the hazard ratio for smoking ≥20 pack-years vs. never smoking is significantly different (at the 5% level) for men vs. women?Most risk factors seem of comparable magnitude
What is the hazard ratio for COPD mortality among men for smokers of ‰¥20 pack-years vs. never smokers? Provide a 95% CI.The results in Table 14.37 were obtained from the study.Table 14.37
Write down the Cox proportional-hazards model. What does the term proportional hazards mean?Pulmonary DiseaseA study was performed among 169,871 Chinese men and women in 1991 ages 40 years and older
What is a hazard rate in the context of this study? Pulmonary DiseaseA study was performed among 169,871 Chinese men and women in 1991 ages 40 years and older [13]. Baseline data were collected
What are the estimated incidence rates in the ASA and control groups? CancerSuppose we wish to study the association between aspirin intake and the incidence of colon cancer. We find that 10% of
Repeat the analyses in Problem 14.39, but account for covariate differences between groups?
Another way to score the visual analog scale is as a categorical variable where ≥50% improvement is considered a success and <50% improvement, remaining the same, or worsening is considered a
Repeat the analysis in Problem 14.37, but account for covariate differences between groups?
If the visual analog scale is treated as a continuous variable, assess whether there are any between-group differences in efficacy without considering the covariates. Try to do at least one analysis
Test the hypothesis that the rate of flu has changed from the 2008−2009 to 2009−2010 winter season. Report a two-tailed p-value?Among 1200 students in one high school in the city, 200 developed a
Provide a 95% CI for the rate estimated in Problem 14.34?Among 1200 students in one high school in the city, 200 developed a new case of influenza over the 90 days from December 21, 2009, to March
What is the estimated incidence rate of flu in the 2009−2010 winter season per 1000 person-months? Among 1200 students in one high school in the city, 200 developed a new case of influenza
Provide a two-sided 95% CI for incidence rate of flu among high-risk students during winter 2008−2009?Infectious DiseaseSuppose the incidence rate of influenza (flu) during the winter of
A group of high-risk high school students was identified in the winter of 2008−2009 who had 3+ previous episodes of influenza before December 21, 2008. There were 20 students in this group, each
Assess the validity of the proportional-hazards assumption in Problems 14.29 and 14.30?One issue is that the groups in Problem 14.27 may not be exactly balanced by age and/or initial level of serum
Answer Problem 14.27 while controlling for possible age and initial-level differences between groups. Consider both parametric and nonparametric survival analysis methods?One issue is that the groups
1. Suppose a serum-creatinine level of ≥1.5 mg/dL is considered a sign of possible kidney toxicity. Use survivalanalysis methods to assess whether there are differences in the incidence of kidney
Estimate the rate ratio for postmenopausal vs. premenopausal women after controlling for age. Provide a 95% CI for the rate ratio?CancerThe data in Table 14.34 provide the relationship between
Assess whether there is a difference between the incidence rate of breast cancer for premenopausal vs. postmenopausal women, while controlling for age. Report a p-value?CancerThe data in Table 14.34
Provide a 95% CI for the underlying rate, based on the observed data in Problem 14.23. Express the answer in units of number of events per 100 person-years?Infectious DiseaseSuppose the rate of
Two hundred subjects are selected randomly from the population and followed for various lengths of time. The average length of follow-up is 1.5 years. Suppose that at the end of the study, the
A person is selected randomly from the population and followed for 1.5 years. If the true rate of allergic reactions is 5 reactions per 100 person-years, what is the probability that the subject will
Divide participants according to median log10CO (adjusted), and estimate survival curves for each subgroup?
Answer Problem 14.39 under this definition of success?To reduce variability, the investigators also considered a criterion of at least 50% improvement on two successive visits as a definition of
Answer Problem 14.40 under this definition of success?To reduce variability, the investigators also considered a criterion of at least 50% improvement on two successive visits as a definition of
Is there a significant difference between these incidence rates? Report a p-value (two-tailed)?CancerSuppose we wish to study the association between aspirin intake and the incidence of colon cancer.
What is the estimated rate ratio for colon cancer between the ASA and placebo groups?CancerSuppose we wish to study the association between aspirin intake and the incidence of colon cancer. We find
Provide a 95% CI for the rate ratio in Problem 14.45?CancerSuppose we wish to study the association between aspirin intake and the incidence of colon cancer. We find that 10% of women take 7 aspirin
Suppose we look at the subset of women with a family history of colon cancer. Aspirin might be more beneficial in this high-risk subgroup. We have a total of 5000 person-years among ASA women and 2
What is the estimated mortality rate and 95% CI per 1000 person-years among current smokers? Health PromotionA recent, article by Kenfield et al. [12] studied the relationship between various
What test can be performed to compare mortality incidence between former smokers who quit <5 years ago vs. current smokers? Health PromotionA recent, article by Kenfield et al. [12] studied
Implement the test in Problem 14.49, and report a p-value (two-tailed)?Health PromotionA recent, article by Kenfield et al. [12] studied the relationship between various aspects of smoking and
What is the estimated rate ratio for total mortality between former smokers who quit 20+ years ago and current smokers? Provide a 95% CI for this estimate?Health PromotionA recent, article by
The age-adjusted rate ratio between the groups in Problem 14.51 was 0.34. Is this different from the estimated rate ratio in Problem 14.51? If so, why?Health PromotionA recent, article by Kenfield et
What does a censored observation in 1992 mean in the context of these data? CancerA study was performed to compare breast cancer incidence between postmenopausal women who used PMH vs. women who
Estimate the 10-year incidence of breast cancer in each group?CancerA study was performed to compare breast cancer incidence between postmenopausal women who used PMH vs. women who did not. A group
What test can be used to compare the incidence of breast cancer between the 2 groups, taking into account the time when breast cancer develops and the length of follow-up of each
Implement the test in Problem 14.55, and report a p-value (two-tailed)?CancerA study was performed to compare breast cancer incidence between postmenopausal women who used PMH vs. women who did not.
How many subjects need to be enrolled in each group (assume equal sample size in each group) to achieve 80% power if a two-sided test is used with Î± = .05 and the same assumptions are
Suppose a new study is planned, with 200 patients randomly assigned to each of a 400 IU per day vitamin E group and a 3 IU per day vitamin E group. If the survival experience in the 3 IU per day
Compare overall survival curves of the two groups, and obtain a p-value?OphthalmologyIn Table 14.33, we present data from the RP clinical trial described in Example 14.30 (on page 813) concerning
Obtain a 95% CI for the survival probability at year 6 for each group?OphthalmologyIn Table 14.33, we present data from the RP clinical trial described in Example 14.30 (on page 813) concerning
Estimate the survival probability by year for each group?OphthalmologyIn Table 14.33, we present data from the RP clinical trial described in Example 14.30 (on page 813) concerning effect of
Estimate the hazard function by year for each group?OphthalmologyIn Table 14.33, we present data from the RP clinical trial described in Example 14.30 (on page 813) concerning effect of high-dose
Answer the same question posed in Problem 14.13 assuming the criterion for bioavailability is a 100% increase in plasma-carotene level from baseline?
Answer the same question as in Problem 14.12 assuming the criterion for bioavailability is a 100% increase in plasma-carotene level from baseline?
Assess whether there are significant differences among the survival curves obtained in Problem 14.12?
Suppose we regard a preparation as being bioavailable for a subject at the first week when level of plasma carotene increases by 50% from the baseline level (based on an average of the first and
Compare the crude and adjusted analyses of the relationship of log10CO to recidivism in Problems 14.8 and 14.9?A Cox proportional-hazards model was fit to these data to assess the relationship
Estimate the effects of each variable in terms of hazard ratios, and provide 95% confidence limits corresponding to each point estimate?A Cox proportional-hazards model was fit to these data to
Assess the significance of each of the variables?A Cox proportional-hazards model was fit to these data to assess the relationship between age, sex, number of cigarettes smoked, and log10CO
Compare survival curves of the two groups, using hypothesis-testing methods, and report a p-value?
What is the expected number of events that need to be realized in each group to achieve 80% power to detect an IRR for breast cancer of 1.5 for current OC users vs. never OC users under the same
How much power did the study have for detecting an IRR for breast cancer of 1.5, comparing current OC users vs. never OC users among 40- to 44-year-old women if(a) The true incidence rate of breast
Estimate the rate ratio comparing past users vs. never users, and provide a 95% CI about this estimate?CancerThe data relating oral-contraceptive (OC) use and the incidence of breast cancer in the
Estimate the rate ratio comparing current users vs. never users, and provide a 95% CI about this estimate?CancerThe data relating oral-contraceptive (OC) use and the incidence of breast cancer in the
Compare the incidence density of breast cancer in past users vs. never users, and report a p-value?CancerThe data relating oral-contraceptive (OC) use and the incidence of breast cancer in the age
Compare the incidence density of breast cancer in current users vs. never users, and report a p-value?CancerThe data relating oral-contraceptive (OC) use and the incidence of breast cancer in the age
Treat testosterone as a categorical variable in quartiles, with the 1st quartile as the reference group?
Discuss your results from Problems 13.115 and 13.116?
For both Caucasians and African Americans (seperately), estimate the OR between late age at menarche (‰¥12) and ovarian cancer risk and provide a 95% CI about these estimate?CancerResults
Estimate the OR for the association between age at menarche and ovarian cancer after controlling for race, and provide a 95% CI about this estimate?Two logistic models were run with Stata Version 11
What does the variable Î²1mean in the 2nd logistic regression (Table 13.63)? How does it differ from the meaning of Î²1in the 1st logistic regression (Table 13.62)? Two
Assess whether the effect of age at menarche is different for Caucasian vs. African American women. Report a p-value (two-tailed)?Two logistic models were run with Stata Version 11 using these data.
13.122 Use polytomous logistic regression with group = 0 as the reference group to assess the association between SBP z-score group and the following variables:(a) BMI,(b) height, (c) region
Use ordinal logistic regression to assess the association between SBP z-score group and the same variables in Problem 13.122?HypertensionThe data set WALES.DAT contains familial data on blood
Compare your results in Problems 13.122 and 13.123?HypertensionThe data set WALES.DAT contains familial data on blood pressure (bp) in two-communities in South Wales (the Rhondda Fach and the Vale of
Repeat the analyses in Problems 13.122€“13.124 using diastolic bp (DBP) z score group defined in the same manner as SBP z-score group?HypertensionThe data set WALES.DAT contains familial
Treat testosterone as a continuous variable (suitably transformed if necessary)?
Evaluate whether age is an effect modifier of the relationship between aspirin and CVD?Cardiovascular DiseaseThe Women€™s Health Study randomly assigned 39,876 initially healthy women ages
Evaluate whether age confounds the CVDˆ’ aspirin relationship by using dummy variables for age categories; calculate the age-adjusted OR estimate and 95% CI?Cardiovascular DiseaseThe
1. Obtain the crude OR estimate, and provide a 95% CI for the crude OR?2. Test the null hypothesis of no association between aspirin assignment and CVD?Cardiovascular DiseaseThe Women€™s
Provide a 95% CI about this estimate?OphthalmologyThe data in Table 13.59 were presented relating body mass index (BMI) to progression of advanced age-related macular degeneration (AMD), a common eye
What is the attributable risk (AR) of high BMI (‰¥25) for progression of AMD? OphthalmologyThe data in Table 13.59 were presented relating body mass index (BMI) to progression of
1. Use logistic regression methods to assess whether there is an association between ovarian cancer risk and duration of OC use while controlling for age. Provide a two-sided p-value. Assume that the

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