Epi Module 2 Practice Questions

Select the type of study which would best be used to evaluate the lead levels, IQ test results, and behavioral scores of children aged 3-5 in New York State. 1 Cross-sectional study 2 Case-control study 3 Cohort Study 4 Clinical Trial

1 - Clinical trials are used to assess the efficacy of new treatments or interventions. Ideally they are conducted in a randomized, double-blind manner. Cross-sectional studies evaluate the characteristics of a population not selected by either exposure or disease. While associations may be observed, causality cannot be determined. Case series reports are useful for describing groups of patients with similar treatments or diseases when there is no control group. The results of these studies are usually not generalizable. Case-control studies compare populations with disease to populations without disease with respect to possible associated factors. They are the studies of choice when information is desired about rare diseases. They are much easier to conduct than cohort studies because they are smaller and less expensive, but they are subject to much greater chance of bias. Cohort studies compare populations with exposure to the agent of interest to populations without such exposure with respect to various outcomes. They are the studies of choice when evaluating the factors possibly responsible for common, chronic diseases. They are large, cumbersome, and expensive, but bias is usually much less of an issue than with case-control studies.

Case-control studies involve the 1 Comparison of diseased and non-diseased populations 2 Comparison of exposed and non-exposed populations 3 Analysis of multiple case reports 4 Analysis of the characteristics of selected populations 5 Comparison of treated and non-treated populations

1- Explanation Case-control studies compare diseased and non-diseased populations for differences in risk factors. Cohort studies compare populations exposed to a particular factor to control populations to assess the development of disease. Case series reports involve the analysis of multiple case reports. Cross-sectional studies involve the analysis of the characteristics of selected populations. Experimental studies involve the comparison of populations after an interventional measure with control groups.

In a cohort study of bacteriuria among elderly residents of a large nursing home, it is found that the incidence of bacteriuria among the female patients is 33 cases per 100 person-years, while that among the male patients is 11 cases per 100 person-years. Calculate the relative risk for bacteriuria among nursing home patients that is associated with being female 1 3.0 2 0.33 3 22 4 0.045 5 The relative risk cannot be calculated without knowing the total sample size

1- Explanation In a cohort study, it is possible to derive true measures of disease incidence in the different groups followed over time. The relative risk is calculated as the ratio of rates found in these different groups (i.e., male and female nursing home patients). The relative risk measures that relative difference in rates between two or more groups, and is expressed without units. It is not necessary to know the total sample size to calculate the relative risk.

In conducting a study of exposure to a popular antihistamine and otherwise unexpected mortality, you review the medical records of persons who have recently died unexpectedly at a large university medical center. You also review the records of surviving individuals who were admitted to the medical center immediately following the deceased patients. In reviewing the medical records, you abstract information on exposure to the antihistamine and other medications, the age of the individual, and other medical and demographic information that you think will be important. You are interested in determining the odds ratio (OR) between exposure to the antihistamine and subsequent mortality. What type of study are you conducting in this example? 1 A case-control study 2 A retrospective cohort study 3 A prospective cohort study 4 A cross-sectional study

1- The study described in the question above is a good example of a case-control study. In a case-control study, cases and controls are enrolled based on their current status (i.e., alive or dead). Information on the exposure is typically ascertained through medical record reviews or patient interviews. In some cases, information gained from laboratory testing of biologic specimens may also be used. Odds ratios (ORs) are typically used to describe the relationship between the exposure(s) and outcome(s) of interest, and p-values may be used to evaluate the statistical significance of the association.

In the analysis of data from epidemiologic studies, it is often desirable to control for the effect of one or more confounders in attempting to measure the true association between the exposure and outcome. When the outcome is dichotomous, multivariate logistic regression modeling is often used to simultaneously control for multiple confounders. In contrast to linear regression models, the beta-coefficient estimate obtained from a logistic regression model can be easily transformed to a readily-interpretable epidemiologic measure. What is this epidemiologic measure? 1 The odds ratio 2 The relative risk 3 The attributable risk 4 The attributable risk percent 5 The proportional mortality ratio

1- n a logistic regression model, the natural logarithm (ln) of the odds is used in the place of simple probabilities. Properly used, the logistic regression model will fit an equation that best predicts the dependent (or outcome) variable from a set of independent (or predictor) variables. After the model has been fit, so-called beta coefficients (β) will be available as output for each of the predictor variables included in the equation. Mathematically, the odds ratio for a given predictor variable (i.e., exposure or confounder) can simply be expressed as e raised to the β power (where e is the base of the natural logarithm, equal to approximately 2.71828, and β is unique for each predictor variable used in the logistic regression model).

Of 2,872 persons who had received radiation treatment in childhood because of an enlarged thymus, cancer of the thyroid developed in 24 and a benign thyroid tumor developed in 52. A comparison group consisted of 5,055 children who had received no such treatment (brothers and sisters of the children who had received radiation treatment). During the follow-up period, none of the comparison group developed thyroid cancer, but benign thyroid tumors developed in six. Calculate the relative risk for benign thyroid tumors: _____

15.3

The case-control study is one type of epidemiologic study which can be used to evaluate the relationship between an exposure and subsequent disease. Which of the following best describes the process by which subjects are selected for a case-control study? 1 Cases and controls are selected based on their exposure status 2 Cases and controls are selected based on their disease status 3 Cases are selected based on their disease status, and controls are selected based on their exposure status 4 Cases are selected based on their exposure status, and controls are selected based on their disease status 5 Cases and controls are selected randomly without regard to exposure or disease status

2 - In a case-control study, cases and controls are selected based on their disease status. Cases are those subjects with the disease (or other outcome of interest), and controls are those without the disease (or other outcome of interest). After selecting an adequate number of cases and controls, the exposure status is ascertained through various means, including the use of biologic specimens, subject interviews, and medical record reviews. In a case-control study, the association between an exposure and subsequent disease is typically described using the odds ratio (OR). Case control studies are retrospective in nature and have three distinct features: both the exposure and the outcome of the disease have already occurred before the start of the study (hence it is retrospective the study proceeds from effect to cause a control or comparison group is used to support or refute an inference Thus case control studies are comparison studies and therefore must have 2 populations - namely the cases and the controls.

The population at risk is: 1 The total number over the specified period 2 The average number over the specified period 3 The average number over a total period 4 The specified period over the average number 5 The specified period over the total number 6 The total period over the total number

2- The population at risk is the average number over the specified period.

Residents of three villages with three different types of water supply were asked to participate in a survey to identify cholera carriers. Because several cholera deaths had occurred recently, virtually everyone present at the time under- went examination. The proportion of residents in each village who were carriers was computed and compared. What is the proper classification for this study? a. Cross-sectional study b. Case-control study c. Prospective cohort study d. Retrospective cohort study e. Experimental study

A

A group of pediatricians is interested in investigating the relationship between day-care attendance and the incidence of severe diaper rash caused by Candida species in children under the age of one year. Two groups of patients were enrolled at the age of two months and were followed until the time of their first birthday. The first group of patients did not attend day-care at all during the first year, while the second group attended day care for between 15 and 45 hours each week. A total of 230 study subjects were enrolled and followed for a total of 1955 person-months. The authors found that the relative risk (RR) for severe Candida diaper rash associated with day-care attendance was 3.4 (95% confidence interval 1.2, 5.6). What is the best description of this type of study 1 A clinical trial 2 A cohort study 3 A case-control study 4 A cross-sectional study

2- This fictional study is a good example of a cohort study. In this type of observational study, subjects are selected based on their exposure (i.e., day-care attendance) and are followed prospectively for the occurrence of selected outcomes. Retrospective cohort studies can also be conducted if the right source(s) of data exists. Relative risks (RR) are often used as the main effect measure for comparing the risk between exposed and unexposed subjects.

An investigator is interested in measuring the association between smoking during pregnancy and the delivery of a low birthweight (LBW) infant. In order to be able to properly evaluate the magnitude and statistical significance of this relationship, the investigator knows that she will have to collect data on potential confounding variables, such as maternal race, as well. Which of the following most fully describes the notion of a confounder in epidemiology? 1 A confounder is associated only with the exposure 2 A confounder is associated only with the disease outcome 3 A confounder must be associated with both the exposure and disease outcome. 4 A confounder must be associated with both the exposure and disease in a statistically significant fashion 5 A confounder can be associated with either the exposure or the disease outcome, but does not need to be associated with both

3 - Explanation In epidemiology, the concept of the confounder (or confounding) is used to describe the situation in which a third variable affects the measurement of the association between the two variables of primary interest (i.e., the exposure and disease outcome). To be a confounder, this third variable must be associated with both exposure and outcome, but not necessarily to a statistically significant degree. A confounder may create the appearance of an association between the exposure and outcome which does not truly exist. Conversely, a confounder may also mask the true relationship between the exposure and outcome, making it appear as if there is no association when one actually does exist. In an epidemiologic investigation into the association between smoking and LBW, it would be typically necessary to treat race as a potential confounder, since the rate of LBW deliveries varies by maternal race, as does the likelihood of smoking during pregnancy.

You are interested in investigating the association between maternal smoking and alcohol consumption during pregnancy and the subsequent risk of reactive airway disease (RAD) for the child from birth to five years. After considering different approaches to this investigation, you decide to enroll 150 women from each of the following groups in your study: pregnant women not smoking or drinking during their pregnancy, pregnant women smoking but not drinking during their pregnancy, pregnant women drinking but not smoking during their pregnancy, and pregnant women smoking and drinking during their pregnancy. After birth, each child is to be followed until the age of five. What is the best description of this study design? 1 A case-control study 2 A retrospective cohort study 3 A prospective cohort study 4 A cross-sectional study 5 A case-crossover study

3 - The study described above is a typical prospective cohort study. The fact that the study is prospective simply indicates that the study subjects are enrolled and followed forward in time. In this example, information on the exposures of interest would most likely be obtained during the pregnancy. Likewise, the outcome information on the children would be obtained from the time of birth to their fifth birthday. In a prospective cohort study, groups with different degrees of exposure are enrolled and followed forward in time. Prospective cohort studies are very useful for calculating the incidence of disease (i.e., reactive airway disease) in groups with differing levels of exposure. Relative risks may also be used to compare the disease incidence between these different groups.

It would be of interest to know whether or not mildly elevated levels of radon in homes causes any long-term adverse health effects, such as lung cancer or heart disease. Which of the following studies would be the best to use to obtain this information? 1 Cross-sectional study 2 Case-control study 3 Cohort Study Clinical trial

3- Clinical trials are used to assess the efficacy of new treatments or interventions. Ideally they are conducted in a randomized, double-blind manner. Cross-sectional studies evaluate the characteristics of a population which is not selected by either exposure or disease. While associations may be observed, causality cannot be determined. Case series reports are useful for describing groups of patients with similar treatments or diseases when there is no control group. The results of these studies are usually not generalizable. Case-control studies compare populations with disease to populations without disease with respect to possible associated factors. They are the studies of choice when information is desired about rare diseases. They are much easier to conduct that cohort studies because they are smaller and less expensive, but they are subject to much greater chance of bias. Cohort studies compare populations with exposure to the agent of interest to populations without such exposure with respect to various outcomes. They are the studies of choice when evaluating the factors possibly responsible for common, chronic diseases. They are large, cumbersome, and expensive, but bias is usually much less of an issue than with case-control studies.

Which of the following statements is true? 1 Adjusted rates are simpler to calculate than crude rates 2 Crude rates are useful for comparing mortality between different populations 3 Adjusted rates are used to calculate standardized ratios 4 Crude rates equalize differences in age between populations 5 Crude rates are calculated from adjusted rates

3- Explanation Crude rates are simply calculated from the number of events and the size of the population. Adjusted rates are more complex because they take into account the demographic composition of populations. Adjusted rates have the advantage of being useful for comparing morbidity and mortality between populations because they adjust crude rates for factors such as age, gender, and race. Standardized ratios are calculated from adjusted rates, and are used to determine whether the frequency of observed events in a population is more or less than expected.

A group of investigators selected 135 subjects with a diagnosis of Alzheimer's Disease (AD) and 145 subjects without a diagnosis of AD or other dementias. After enrolling these subjects, the investigators interviewed the patients and their family members, and they searched their medical records for evidence of long-term use of non-steroidal anti-inflammatory drugs (NSAIDs). As of result of data collected during this study, the authors concluded that those patients with long-term exposure to NSAIDs were less likely to have AD (odds ratio 0.7, 95% confidence interval 0.58-0.94).What is the best description of this type of study? 1 Clinical trial 2 Cohort study 3 Case-control study 4 Cross-sectional study 5 Case series

3- This fictional study is a good example of the case-control study. In the case-control study, patients are selected based on their outcome (or disease) status (e.g., the presence or absence of Alzheimer's Disease). Information on exposure status (exposed vs unexposed) is then gathered through computerized records, medical chart reviews, questionnaires, laboratory assays, or some other means. The odds ratio (OR) is used as the primary measure of effect for most case-control studies.

In a cohort study of smoking and lung cancer, the incidence of lung cancer among smokers was found to be 9/1,000 and the incidence among nonsmokers was 1/1,000. From another source we know that 45% of the total population were smokers. The incidence of lung cancer attributable to smoking in the total population is: ______

3.6/1000

In 1997, Schiodt et al. reported on a study that was conducted at an urban county hospital during a 40-month period (from 1992 to 1995). In this study, patients were identified who were hospitalized for excessive ingestion of acetaminophen. Patients were divided into two groups, those who had attempted to commit suicide, and those whose excessive acetaminophen exposure was a result of accidental ingestion. The authors compared various characteristics (i.e., age, sex, race, intravenous drug use history, etc.) between the two groups (accidental exposure patients vs. suicide attempting patients), and found that patients hospitalized because of accidental misuse of acetaminophen had a higher prevalence of morbidity and mortality. Odds ratios (OR) and the Student's unpaired t-test were used to compare the two groups. What is the best description of this study 1 A clinical trial 2 A cohort study 3 A case-control study 4 A cross-sectional study

4 - This is an example of a cross-sectional study. In this study, data was collected on a total of 71 patients divided into two groups. The groups were compared in a cross-sectional fashion to discern potentially important differences between those with intentional and accidental exposure to acetaminophen. Even though this study was conducted over a three-year period, this study is not a cohort study, since the patients were not followed over time. Cross-sectional studies are best suited for estimates of disease prevalence and for evaluating static associations. Measures of disease incidence and true relative risks cannot be derived from cross-sectional (or case-control) studies.

A study reported on data that was analyzed from a survey of students in grades 9-12 in Massachusetts. The authors were interested in the association between suicide attempts and other behaviors, such as sexual activity, substance use, and violence. The authors found that attempting suicide was associated with some of these other behaviors.What is the best description of this type of study? 1 Clinical trial 2 Cohort study 3 Case-control study 4 Cross-sectional study 5 Case series

4 - This study is an example of a cross-sectional study. In a cross-sectional study, the investigators are typically interested in the association between two or more factors (such as suicide and substance abuse). The association between these factors is usually reported with odds ratios or other simple measures of association. While cross-sectional studies are usually a reasonable starting point for collecting pilot data, there are many important questions that cannot be addressed with cross-sectional data, including causality, timing, and estimates of incidence.

hat does attributable risk measure? 1 The likelihood that a positive result is due to chance 2 The relative risk of disease occurring due to certain factors 3 The amount of disease existing in a population at a certain point in time 4 The difference in occurrence of disease between exposed and unexposed populations 5 Additional risk secondary to confounding variables

4- Attributable risk, which can be determined from cohort studies, is a measure of the difference in occurrence of disease between exposed and unexposed populations. The likelihood that a positive result is due to chance is a measure of type I (α) error. Prevalence is the amount of disease existing in a population at a certain point in time. The odds ratio is a measure of the estimated relative risk occurring due to certain factors. Confounding variables may cause bias in studies.

You are asked to help consult on a study which was recently completed in a coastal African country. In this study, a total of 274 soldiers stationed in three different camps were examined and tested for the presence of bacterial sexually transmitted diseases (STD) and human immunodeficiency virus (HIV) positivity. In addition to the information from the clinical exam and laboratory specimens, interviews were conducted to gather information on age, years of military service, ethnicity, and region of origin. The data are now to be analyzed to learn which factors were associated with the presence of STDs, including HIV. What is the most accurate description of this study design? 1 A case-control study 2 A cohort study 3 A clinical trial 4 A cross-sectional study 5 A case-cohort study

4- In a cross-sectional study, a variety of independent variables can be studied for their association with the outcome variables. In this example, the independent variables would include age, years of military service, ethnicity, and region of origin. The outcome variables include the presence of bacterial sexually transmitted diseases (STDs) and HIV positivity. This study does not meet the criteria for being a case-control, cohort, or case-cohort study, nor is it a clinical trial. The cross-sectional study is limited in its power, and valid inferences may be especially difficult to make from cross-sectional studies, even when statistically significant associations are observed.

Which of the following is not an advantage of a prospect of cohort study A. It usually cost less than a case control study B. Precise measurement of exposure as possible C. Incidence rate can be calculated D. Recall by us as minimalize compared with a case control study E. Many disease outcomes could be studied simultaneously

A

A patient is participating in a population-based study of exposure to a particular medication and fatal myocardial infarction. In this study, each case will actually be able to serve as its own control, dramatically reducing the sample size necessary to carry out this study. While a given individual is exposed to the medication, they will accrue time as a case; and while not exposed to the medication in concern, each individual will accrue time as a control.What best describes this research 1 A case-control study 2 A retrospective cohort study 3 A prospective cohort study 4 A cross-sectional study 5 A case-crossover study

5 - In the case-crossover study, each patient serves as their own control, usually resulting in a reduction of the sample size necessary to properly conduct the study. In this example, when patients are taking the medication in concern, they will accrue time as a case. Similarly, when not taking the medication they will accrue time as a control. Proper design and analysis of the case-crossover study will usually require consultation with an epidemiologist or biostatistician. The case-crossover design is often well-suited to questions of pharmacoepidemiology.

In 1995, Levin et al. reported on a total of six children with disseminated atypical mycobacterial infection in the absence of any recognized immunodeficiency. The children had presented with complaints of fever, weight loss, and lymphadenopathy. In the report, the authors characterized the difference species of Mycobacterium infecting these children, and also described diminished T-cell proliferative responses. Which of the following best describes this type of study? 1 A clinical trial 2 A cohort study 3 A case-control study 4 A cross-sectional study 5 A case series

5 - This study by Levin et al. is a good example of a case series. The purpose of the case series is to call attention to a rare or previously unreported medical condition. Often case series contain observations on a small number of individuals, with quite detailed descriptions of the patients studied. Case series (and case reports) can lead to larger epidemiologic studies, and may provide early clues to important medical and scientific discoveries. However, the inferences that can be made from case series are limited, and over-generalization from case series or case reports should be avoided.

In a cohort study of smoking and lung cancer, the incidence of lung cancer among smokers was found to be 9/1,000 and the incidence among nonsmokers was 1/1,000. From another source we know that 45% of the total population were smokers.The proportion of the risk in the total population that is attributable to smoking is: ______

78.3%

A major problem resulting from the lack of randomization in a cohort study is A. The possibility that a factor that led to the exposure rather than the exposure itself might have caused the disease B. The possibility that a greater proportion of people in the study may have been exposed to C. The possibility that a smaller proportion of people in the study may have been exposed D. That without randomization the study may take longer to carry out E. Planned crossover is more likely

A

An investigator examined cases of fetal death in 27,000 pregnancies and classified mothers according to whether they had experienced sexual intercourse within 1 month before delivery. It was found that 11% of the mothers of fetuses that died and 2.5% of the mothers of fetuses that survived had had sexual intercourse during the period. It was concluded that intercourse during the month preceding delivery caused the fetal deaths. This conclusion: a. May be incorrect because mothers who had intercourse during the month before childbirth may differ in other important characteristics from those who did not b. May be incorrect because there is no comparison group c. May be incorrect because prevalence rates are used where incidence rates are needed d. May be incorrect because of failure to achieve a high level of statistical significance e. Both b and c

A

Retrospective cohort studies are characterized by all of the following except A. The study groups are exposed and unexposed B. Incidence rates may be computed C. The required sample size is smaller than that need it for a prospect of cohort study to line the required sample size is similar to that need it for a prospect of cohort study D. They are useful for rare exposures

C

Which of the following is a case-control study? a. Study of past mortality or morbidity trends to permit estimates of the occurrence of disease in the future b. Analysis of previous research in different places and under different circumstances to permit the establishment of hypotheses based on cumulative knowledge of all known factors c.Obtaining histories and other information from a group of known cases and from a comparison group to determine the relative frequency of a characteristic or exposure under study d. Study of the incidence of cancer in men who have quit smoking e. Both a and c

C

In a large case-control study of patients with pancreatic cancer, 17% of the patients were found to be diabetic at the time of diagnosis, compared with 4% of a well-matched control group (matched by age, sex, ethnic group, and several other characteristics) that was examined for diabetes at the same time as the cases were diagnosed. It was concluded that the diabetes played a causal role in the pancreatic cancer. This conclusion: a. Is correct b. May be incorrect because there is no control or comparison group c. May be incorrect because of failure to establish the time sequence between onset of the diabetes and diagnosis of pancreatic cancer d. May be incorrect because of less complete ascertainment of diabetes in the pancreatic cancer cases e. May be incorrect because of more complete ascertainment of pancreatic cancer in nondiabetic persons

C

Factor A, B, or C can each individually cause a certain disease without the other two factors but only when fol- lowed by exposure to factor X. Exposure to factor X alone is not followed by the disease, but the disease never occurs in the absence of exposure to factor X. Factor X is: a. A necessary and sufficient cause b. A necessary but not sufficient cause c. A sufficient but not necessary cause d. Neither necessary nor sufficient e. None of the above

B

In a study begun in 1965, a group of 3,000 adults in Baltimore were asked about alcohol consumption. The occur- rence of cases of cancer between 1981 and 1995 was studied in this group. This is an example of: a. A cross-sectional study b. A prospective cohort study c. A retrospective cohort study d. A clinical trial e. A case-control study

B

several studies have found that approximately 85% of cases of lung cancer are due to cigarette smoking. This measure is an example of: a. An incidence rate b. An attributable risk c. A relative risk d. A prevalence risk e. A proportionate mortality ratio

B

A case-control study is characterized by all of the following except: a. It is relatively inexpensive compared with most other epidemiologic study designs b. Patients with the disease (cases) are compared with persons without the disease (controls) c. Incidence rates may be computed directly d. Assessment of past exposure may be biased e. Definition of cases may be difficult

C

A researcher wants to investigate if tea consumption (assessed by a biomarker for tea metabolism) increases the risk of CHD. He uses a case-control study to answer this question. CHD is rare in younger people. Which two groups are best to enroll and compare for this purpose? a. The group of CHD cases and a group of those who do not have CHD individually matched to the cases for tea metabolism biomarker b. The group of CHD cases and a group of those who do not have CHD frequency matched to the cases for tea metabolism biomarker c. The group of CHD cases and a group of those who do not develop CHD, matched for age d.A random sample of those who drink tea and a random sample of those who do not drink tea, matched for age e. A random sample of those who drink tea and a random sample of those who do not drink tea, unmatched for age

C

Ecologic fallacy refers to: a. Assessing exposure in large groups rather than in many small groups b. Assessing outcome in large groups rather than in many small groups c. Ascribing the characteristics of a group to every individual in that group d. Examining correlations of exposure and outcomes rather than time trends e. Failure to examine temporal relationships between exposures and outcomes

C

In a cohort study the advantage of starting by selecting a defined population for study before any of its members became exposed rather than starting by Selecting exposed and unexposed individuals is that A. I said he can be completed more rapidly B. A number of outcomes can be studied simultaneously C. A number of exposures can be studied simultaneously D. The study will cost less to carry out E. A&D

C

In a small pilot study, 12 women with endometrial cancer (cancer of the uterus) and 12 women with no apparent disease were contacted and asked whether they had ever used estrogen. Each woman with cancer was matched by age, race, weight, and parity to a woman without disease. What kind of study design is this? a. Prospective cohort study b. Retrospective cohort study c. Case-control study d. Cross-sectional study e. Experimental study

C

Which of the following is a true conclusion concerning matching? a. Once we have matched controls to cases according to a given characteristic, we can only study that characteristic when the prevalence of disease is low b. If an attempt is made to match on too many characteristics, it may prove difficult or impossible to adjust for all of the characteristics during data analysis c. Matching on many variables may make it difficult to find an appropriate control d. Individual matching differs from frequency matching because controls are selected from hospitals instead of from the general population e. None of the above

C

Factor A, B, or C can each individually cause a certain disease without the other two factors but only when fol- lowed by exposure to factor X. Exposure to factor X alone is not followed by the disease, but the disease never occurs in the absence of exposure to factor X. Factor A is: a. A necessary and sufficient cause b. A necessary but not sufficient cause c. A sufficient but not necessary cause d. Neither necessary nor sufficient e. None of the above

D

In 2010 investigators were interested in studying early Adele obesity is a risk factor for cancer mortality. The investigators obtain physician health report on students who attended the University of Glasgow between 1948 1968 these reports included records of the students hated weights at the time they attended the University. The students were than fall through 2010. Mortality information was obtained using death certificates. The study can be best described as A. Nested case control B. Cross-sectional C. Prospect of cohort D. Retrospective cohort E. Population-based cased control

D

In cohort studies of the role of a suspected factor in the ideology of a disease it is essential that A. There be an equal number of persons in both study groups B. At the beginning of the study those with the disease in those without the disease have the equal risk of having the factor C. The study group with the factor in the study group without the factor be representative of the general population D. The expose expose groups understudy be a similar as possible with regard to possible confounding factors E. Both b and C

D

In which one of the following types of study designs does a subject serve as his own control? a. Prospective cohort study b. Retrospective cohort study c. Case-cohort study D. case crossover study E. Case control study

D

The physical examination records of the entire incoming freshman class of 1935 at the University of Minnesota were examined in 1977 to see if their recorded height and weight at the time of admission to the university was related to the development of coronary heart disease (CHD) by 1986. This is an example of: a. A cross-sectional study b. A case-control study c. A prospective cohort study d. A retrospective cohort study e. An experimental study

D

All of the following are important criteria when making causal inferences except: a. Consistency with existing knowledge b. Dose-response relationship c. Consistency of association in several studies d. Strength of association e. Predictive value

E

From 1983 to 1988 blood samples were obtained from 3450 HIV negative men in the multi center each cohort study and stored in a national repository. In 2010 a researcher was interested in examining the association between levels of inflammation and HIV infection. Of the 3450 men 660 men were identified as HIV infected cases. The researchers investigated the association between CRP and HIV infection among the 660 cases and 660 controls matched to the cases by agent at the city who did not become infected with HIV. The researcher used to control blood samples to measure the serum level of CRP. The study initiated in 2010 is an example of A. Nested case cohort study B. Nested case control study C. Retrospective cohort study D. Cross-sectional study E. Randomized clinical trial

E

In a case-control study, which of the following is true? a. The proportion of cases with the exposure is compared with the proportion of controls with the exposure b. Disease rates are compared for people with the factor of interest and for people without the factor of interest c. The investigator may choose to have multiple comparison groups d. Recall bias is a potential problem e. a, c, and d

E

In a study of a disease in which all cases that developed were ascertained, if the relative risk for the association between a factor and the disease is equal to or less than 1.0, then: a. There is no association between the factor and the disease b. The factor protects against development of the disease c. Either matching or randomization has been unsuccessful d. The comparison group used was unsuitable, and a valid comparison is not possible e. There is either no association or a negative association between the factor and the disease

E