PUBH 6035 Module 7 Final Exam

1. Question: What were the total person-months at risk during the study? 2. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4-year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the risk ratio (a.k.a. relative risk) using the given data. The numeric value of the risk ratio is... 3. Question: A randomized experimental study was conducted to evaluate the effectiveness of a new pertussis vaccine. One thousand healthy children were randomized to receive either the new vaccine (500 children) or the old vaccine (500 children). The children were followed for two years to monitor the incidence of pertussis. At the end of the study, the risk ratio for developing pertussis was 0.5 among the children who received the new vaccine compared to children who received the old vaccine. The 95% confidence interval for this relative risk was 0.2-0.8 and the p value was 0.01. State in words your interpretation of the risk ratio. 4. Question: Suppose that you began a one-year study of tuberculosis (TB) on January 1st, 2013. You enrolled 500 residents in your study and checked on their TB status on a monthly basis. At the start of your study on January 1st, you screened all 500 residents. 30 residents already had existing cases of TB on January 1st. On February 1st, 5 residents developed TB. On April 1st, 5 more residents developed TB. On July 1st, 10 of the residents who had existing TB on January 1st died from their disease. The study ended on December 31, 2010. Assume that once a person gets TB, they have it for the duration of the study, and assume that all remaining residents stayed healthy and were not lost to follow-up. What was the case- fatality rate among residents with TB over the course of the year? 5. Question: Three principles guide research that involves human participants. These are: 6. Question: Which letters of the diagram are associated with the starting and stopping points for the lead time for this individual? 7. Question: A case-control study was conducted to identify risk factors for the common cold. Living with children under the age of 10 was one of the risk factors evaluated. The odds ratio for this association was 9.0 and the 95% confidence interval ranged from 1.2 to 85. Which of the following statements is true about this association? Choose all that apply. 8. Question: Suppose that we undertake a cohort study to examine the association of high salt intake and hypertension. Our study population consists of male and female Hispanics and Caucasians. No matching or restriction is performed. Let's assume that the following facts are true: Men consume more salt than women. Irrespective of their salt consumption, men have a greater risk of developing hypertension than women. Smokers consume the same amount of salt as non-smokers. Smoking is an independent risk factor for hypertension. Hispanics consume more salt than Caucasians. Irrespective of their salt consumption , Hispanics have the same risk of hypertension as Caucasians. Based on the above information, which of the following are likely confounders in this study? 9. Question: In January 2001 forty heterosexual hemophiliac patients (all males) were asked to participate in a 3-year prospective study . The men were to undergo an interview, physical examination, and blood testing for HIV status every 6 months for 3 years. Among the 40 subjects there were 30 who were seronegative and healthy for the entire duration of the study, and all of these were followed for the entire 3 years. During the initial screening, 2 of the men were found to already be HIV+, although none of them had clinical signs of AIDS. The table below describes the 10 subjects who either tested HIV positive, or became lost to follow-up, or already were HIV positive at the start of the study. 10. Question: A study followed 900,000 US adults from 1992 to 2008. At baseline, all participants were screened and determined to be cancer free, and their body mass index (BMI) was calculated. Body mass index is a measure of obesity that is calculated using a person's height and weight. Subjects were separated into the following groups according to their BMI: (a) normal weight, (b) slightly overweight, (c) moderately overweight and (d) greatly overweight. 57,145 deaths from cancer occurred in the population during the follow-up period. Calculate the cumulative incidence of deaths from cancer among the study population over the follow-up period. 11. Question: When assessing the results of a study, what are the possible explanations for the observed results? (CHOOSE ALL THAT APPLY) 12. Question: Which type of measure of disease frequency best describes the following: the percentage of healthy, at- risk children in a daycare who develop impetigo (a skin disease) during March 2012. 13. Question: A population of 1,000 healthy, at-risk people is monitored for one year starting on January 1st and the development of cases of chicken pox is noted. No one has chicken pox at the start of the investigation. Twenty people develop chicken pox on June 30th and forty people develop chicken pox on September 30th. Twenty-four people were lost to follow-up on March 31st and twenty-four people were lost to follow-up on November 30th. None of those lost to follow-up had developed chicken pox prior to becoming lost. Assume that you can get chicken pox only once. What is the cumulative incidence of chicken pox in this population during the one-year period from January 1st through December 31st? 14. Question: What is the main limitation of a case series? 15. Question: Consider the situation in a case-control study where the crude odds ratio is 4.6. The data are then divided into two groups. In the first group the group-specific odds ratio is 1.0, and the second group's odds ratio is 3.0. Which of the following is present? 16. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4-year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Which of the following is the correct interpretation of the population risk difference calculated from this study? 17. Question: The risk difference associated with cigarette smoking is much higher for coronary heart disease than lung cancer. This is because coronary heart disease is a much more common disease than lung cancer. 18. Question: Suppose that your company has just developed a new screening test for a disease, and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the specificity of the new screening test: 19. Question: The ideal comparison group in a cohort study... 20. Question: What would happen to the predictive value positive if a screening test were administered in a population with a disease prevalence of 1% instead of 30%? (Assume that the sensitivity and specificity of the test remain the same.) 21. Question: If an exposure has no association with an outcome, then the odds ratio will be 1. 22. Question: Which measure of disease frequency best describes the following: the number of healthy, at-risk women in the Black Women's Health Study who develop hypertension during 121,600 person-years of follow-up. 23. Question: A study followed 900,000 US adults from 1992 to 2008. At baseline, all participants were screened and determined to be cancer free, and their body mass index (BMI) was calculated. Body mass index is a measure of obesity that is calculated using a person's height and weight. Subjects were separated into the following groups according to their BMI: (a) normal weight, (b) slightly overweight, (c) moderately overweight and (d) greatly overweight. 57,145 deaths from cancer occurred in the population during the follow-up period. What type of study is this? 24. Question: What type of observational study design is best suited to study a disease that has a long latent and induction period? (CHOOSE ALL THAT APPLY) 25. Question: Consider the situation in a cohort study where the crude risk ratio is 2.5. The data are then divided into two groups. In the first group the group-specific risk ratio is 1.0, and the second group's risk ratio is 4.0. Which of the following is present? 26. Question: What can randomization do that no other method to control confounding can do? 27. Question: Investigators began a study in 1995 to evaluate the association between infertility treatment and ovarian cancer occurrence among 3,000 Rhode Island women treated for infertility between 1984 and 1994. Cancer incidence was determined by matching the women to information in the Rhode Island Cancer Registry. The cancer rates in this sample were compared with cancer rates among the population of Rhode Island women. What kind of cohort study is this? 28. Question: In 2013, the number of new cases of influenza was 250 in Somerville and 1,075 in Boston. Which city had a higher cumulative incidence of influenza in 2013? 29. Question: A study was conducted on the relationship between folic acid supplementation during pregnancy and the risk of having a child with a neural tube defect. The risk ratio comparing supplemented versus non- supplemented women was 0.33. This means that women who take folic acid were 67% less likely to have a child with a neural tube defect. 30. Question: Differential misclassification can bias study results in which direction? 31. Question: A report of a clinical trial of a new drug versus a placebo noted that the new drug gave a higher proportion of successes than did the placebo (70% versus 40%). The report ended with the statement that the p value associated with this finding was equal to 0.05. This means that 5 out of 100 patients did not benefit from the new drug. 32. Question: A population of 1,000 healthy, at risk people is monitored for one year starting on January 1st and the development of chicken pox cases is noted. No one has chicken pox at the start of the investigation. Twenty people develop chicken pox on June 30th and forty people develop chicken pox on September 30th. Twenty-four people were lost to follow-up on March 31st and twenty-four people were lost to follow-up on November 30th. None of those lost to follow-up had developed chicken pox prior to becoming lost. Assume that you can get chicken pox only once. What is the incidence rate of chicken pox in this population during the one-year period from January 1st through December 31st? 33. Question: Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the sensitivity of the new screening test: 34. Question: Which measure of association is commonly used by public health officials to determine which exposures are most important to the entire population and helps prioritize prevention activities? 35. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the population risk difference using the given data. The numeric value of the population risk difference is... 36. Question: A case-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. 200 cases with brain cancer were identified from the state cancer registry and 200 controls were recruited from the same neighborhoods where the cases lived. The mothers of the children completed a questionnaire that asked them to describe their child's past history of head injury. The investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of the cases while a past history of head injury was reported in 30 of the controls. What type of bias was likely to have influenced the findings of this study? 37. Question: A cohort study was conducted to examine cigarette smoking and the risk of oral cancer. The investigators selected exposed and unexposed subjects so that they had the exactly same distribution of race. This method to address confounding by race is called: 38. Question: Each activity below has a specific purpose in epidemiological research. Match each activity the first column with its corresponding purpose in the second column by selecting the correct letter. You may use an item more than once. If there is more than one correct answer, please give them all. 39. Question: An epidemiological study involved the comparison of per capita annual income and annual rate of teenage pregnancy in Massachusetts counties in 2012. What type of study is this? 40. Question: If an exposure has no association with an outcome, then the attributable proportion in the exposed is 1. 41. Question: In January, 2001 forty heterosexual hemophiliac patients (all males) were asked to participate in a 3 year prospective study . The men were to undergo an interview, physical examination, and blood testing for HIV status every 6 months for 3 years. Among the 40 subjects there were 30 who were seronegative and healthy for the entire duration of the study, and all of these were followed for the entire 3 years. During the initial screening, 2 of the men were found to already be HIV+, although none of them had clinical signs of AIDS. The table below describes the 10 subjects who either tested HIV positive, or became lost to follow-up, or already were HIV positive at the start of the study. Legend: HIV+......What was the cumulative incidence of seropositivity (HIV+) during the 3 year study? a. 5/40 b. 3/10 c. 5/35 d. 3/38 42. Question: What is the main limitation of a case series? 43. Question: Which of the following is an example of incidence rate? the number of newly diagnosed breast cancer cases diagnosed during 200 person-years of follow-up the number of men who were found to have high blood pressure at their yearly physical exam the percentage of infants born with spina bifida (a type of birth defect) among 1,000 liveborn infants 44. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Which of the following is the correct interpretation of the population risk difference calculated from this study? 45. Question: Which measure of disease frequency best describes the following: the number of healthy, at risk women in the Black Women’s Health Study who develop hypertension during 121,600 person- years of follow-up. 46. Question: Which of the following is an example of a “fixed” population? 47. Question: What can randomization do that no other method to control confounding can do? 48. Question: in January, 2001 forty heterosexual hemophiliac patients (all males) were asked to participate in a 3 year prospective study . The men were to undergo an interview, physical examination, and blood testing for HIV status every 6 months for 3 years. Among the 40 subjects there were 30 who were seronegative and healthy for the entire duration of the study, and all of these were followed for the entire 3 years. During the initial screening, 2 of the men were found to already be HIV+, although none of them had clinical signs of AIDS. The table below describes the 10 subjects who either tested HIV positive, or became lost to follow-up, or already were HIV positive at the start of the study. Legend: HIV+ ...... June 2003 HIV+– ? ——— ? ——— ? ——— ? From the information above, what was the prevalence of seropositivity 49. Question: (HIV+) in Jan. 2002? 1. Three principles guide research that involves human participants. 50. Question: If an exposure has no association with an outcome, then the odds ratio will be 1. true or false 51. Question: In January, 2001 forty heterosexual hemophiliac patients (all males) were asked to participate in a 3 year prospective study . The men were to undergo an interview, physical examination, and blood testing for HIV status every 6 months for 3 years. Among the 40 subjects there were 30 who were seronegative and healthy for the entire duration of the study, and all of these were followed for the entire 3 years. During the initial screening, 2 of the men were found to already be HIV+, although none of them had clinical signs of AIDS. The table below describes the 10 subjects who either tested HIV positive, or became lost to follow-up, or already were HIV positive at the start of the study. Legend: HIV+ = found to be HIV+ at the very beginning of the interval observation period ? = lost to follow-up Subject # Initial Screening ..... HIV+– ? ——— ? ——— ? ——— ? What were the total person-months at risk during the study? 52. Question: Which measure of disease frequency best describes the following: the percentage of nursing home residents who have bed sores on July 1, 2012. 53. Question: Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the specificity of the new screening test: 54. Question: Differential misclassification can bias study results in which direction? 55. Question: A study was conducted on the relationship between folic acid supplementation during pregnancy and the risk of having a child with a neural tube defect. The risk ratio comparing supplemented versus non-supplemented women was 0.33. This means that women who take folic acid were 67% less likely to have a child with a neural tube defect. true or false 56. Question: The ideal comparison group in a cohort study… 57. Question: What would happen to the predictive value positive if a screening test were administered in a population with a disease prevalence of 1% instead of 30%? (Assume that the sensitivity and specificity of the test remain the same.) 58. Question: A case-control study was conducted to evaluate the relationship between aspirin use and the risk of colon cancer. 2,000 cases and 2,000 controls were enrolled in the study. 1,800 of the cases reported using aspirin in the past while 1,200 of the controls reported using aspirin in the past. What measure of association should be calculated to determine the strength of the relationship between aspirin and colon cancer? 59. Question: Suppose that we undertake a cohort study to examine the association of high salt intake and hypertension. Our study population consists of male and female Hispanics and Caucasians. No matching or restriction is performed. Let’s assume that the following facts are true: Men consume more salt than women. Irrespective of their salt consumption, men have a greater risk of developing hypertension than women. Smokers consume the same amount of salt as non- smokers. Smoking is an independent risk factor for hypertension. Hispanics consume more salt than Caucasians. Irrespective of their salt consumption , Hispanics have the same risk of hypertension as Caucasians. Based on the above information, which of the following are likely confounders in this study? 60. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the risk ratio (a.k.a. relative risk) using the given data. The numeric value of the risk ratio is… 61. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the population risk difference using the given data. The numeric value of the population risk difference is… 62. Question: What type of observational study design is best suited to study a disease that has a long latent and induction period? (CHOOSE ALL THAT APPLY) 63. Question: A population of 1,000 healthy, at risk people is monitored for one year starting on January 1st and the development of chicken pox cases is noted. No one has chicken pox at the start of the investigation. Twenty people develop chicken pox on June 30th and forty people develop chicken pox on September 30th. Twenty-four people were lost to follow-up on March 31st and twenty-four people were lost to follow-up on November 30th. None of those lost to follow-up had developed chicken pox prior to becoming lost. Assume that you can get chicken pox only once. What is the incidence rate of chicken pox in this population during the one-year period from January 1st through December 31st? 64. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. What was the cumulative incidence of anxiety among coffee drinkers? 65. Question: A population of 1,000 healthy, at risk people is monitored for one year starting on January 1st and the development of cases of chicken pox is noted. No one has chicken pox at the start of the investigation. Twenty people develop chicken pox on June 30th and forty people develop chicken pox on September 30th. Twenty-four people were lost to follow-up on March 31st and twenty-four people were lost to follow-up on November 30th. None of those lost to follow-up had developed chicken pox prior to becoming lost. Assume that you can get chicken pox only once. What is the cumulative incidence of chicken pox in this population during the one-year period from January 1st through December 31st? 66. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Which of the following is the correct interpretation of a risk ratio calculated from this study? 67. Question: Which of the following methods can be used to minimize recall bias in a case-control study? (CHOOSE ALL THAT APPLY) 68. Question: In an experimental study design, when the study participants do not know if they are in the treatment or comparison group but the investigators do, this is called a: 69. Question: Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the predictive value of a positive test: 70. Question: Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. Calculate the sensitivity of the new screening test: 71. Question: Which type of measure of disease frequency best describes the following: the percentage of healthy, at-risk children in a daycare who develop impetigo (a skin disease) during March 2012. 72. Question: Consider the situation in a cohort study where the crude risk ratio is 2.5. The data are then divided into two groups. In the first group the group-specific risk ratio is 1.0, and the second group’s risk ratio is 4.0. Which of the following is present? 73. Question: Investigators began a study in 1995 to evaluate the association between infertility treatment and ovarian cancer occurrence among 3,000 Rhode Island women treated for infertility between 1984 and 1994. Cancer incidence was determined by matching the women to information in the Rhode Island Cancer Registry. The cancer rates in this sample were compared with cancer rates among the population of Rhode Island women. What kind of cohort study is this? 74. Question: Consider the situation in a case-control study where the crude odds ratio is 4.6. The data are then divided into two groups. In the first group the group-specific odds ratio is 1.0, and the second group’s odds ratio is 3.0. Which of the following is present? 75. Question: A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. Calculate the risk difference using the given data. The numeric value of the risk difference is… 76. Question: Suppose that you began a one-year study of tuberculosis (TB) on January 1st, 2013. You enrolled 500 residents in your study and checked on their TB status on a monthly basis. At the start of your study on January 1st, you screened all 500 residents. 30 residents already had existing cases of TB on January 1st. On February 1st, 5 residents developed TB. On April 1st, 5 more residents developed TB. On July 1st, 10 of the residents who had existing TB on January 1st died from their disease. The study ended on December 31, 2010. Assume that once a person gets TB, they have it for the duration of the study, and assume that all remaining residents stayed healthy and were not lost to follow-up. What was the case-fatality rate among residents with TB over the course of the year?