Question 1

Cumulative incidence or average risk is typically used as the measure of disease frequency with which type of cohort because there are no losses to follow-up?

Accepted Answer

A closed cohort is one where no new participants are added after the start, and there are no losses to follow-up, making cumulative incidence an appropriate measure of disease frequency.

Question 2

Which of the following are used in experimental studies to match as closely as possible the experiences of the experimental and comparison groups to permit masking of study investigators?

Accepted Answer

Placebos are used in experimental studies to ensure that the experiences of the experimental and comparison groups are as similar as possible, allowing for the masking of study investigators and participants to reduce bias.

Question 3

A special cohort would be assembled to examine the effects of which of the following?

Accepted Answer

B

Question 4

Although there are several advantages to using the general population as a comparison group, which of the following is the main disadvantage?

Accepted Answer

The healthy worker effect is a main disadvantage when using the general population as a comparison group because employed individuals tend to be healthier than the general population, which includes those who are unemployed due to illness.

Question 5

A comparison group consisting of exactly the same individuals as those in the exposed group had they not been exposed is an example of which theoretical concept?

Accepted Answer

The counterfactual ideal refers to the concept of comparing the same individuals in both exposed and unexposed scenarios to determine the true effect of the exposure.

Question 6

Calculating which measure involves determining the amount of person-time accrued by each study subject?

Accepted Answer

The incidence rate involves calculating the amount of person-time at risk, which requires determining the amount of time each study subject is observed and at risk of developing the outcome.

Question 7

All of the information in a proportional mortality ratio (PMR) study comes from which source?

Accepted Answer

PMR studies use death certificates to determine the proportion of deaths due to specific causes relative to all deaths.

Question 8

Observational studies take advantage of the fact that people expose themselves to noxious or healthy substances through their personal habits.

Accepted Answer

Observational studies involve monitoring subjects in their natural settings without intervention, allowing researchers to study the effects of personal habits and exposures on health outcomes.

Question 9

In an ambidirectional cohort study, both the exposures and outcomes have already occurred by the time the study begins.

Accepted Answer

An ambidirectional cohort study involves both retrospective and prospective elements, meaning some data on exposures or outcomes may be collected before the study begins, but not all outcomes have occurred.

Question 10

Prospective cohort studies are more efficient than retrospective studies for investigating diseases that take a long time to develop and come to a diagnosis.

Accepted Answer

The answer of Prospective cohort studies are more efficient than...

Question 11

Exposures in which type of cohort do not change over time and are followed from a defined starting point to a defined ending point but may suffer from losses to follow-up?

Accepted Answer

A fixed cohort is one where the exposures do not change over time, and the group is followed from a defined starting point to a defined ending point. However, it can suffer from losses to follow-up.

Question 12

Which of the following is the appropriate measure of disease frequency in a fixed cohort when the population experiences losses to follow-up?

Accepted Answer

Incidence rates are appropriate for a fixed cohort with losses to follow-up because they account for the time each individual is at risk, allowing for accurate measurement despite varying follow-up times.

Question 13

Which of the following is assembled to study the health effects of rare exposures, such as uncommon occupational chemicals?

Accepted Answer

A special cohort is assembled to study the health effects of rare exposures, as it focuses on specific groups with uncommon characteristics or exposures.

Question 14

Which of the following is often selected from professional groups such as doctors and nurses, volunteers, or residents in well-defined geographic areas to facilitate follow-up and accurate ascertainment of the outcomes under study?

Accepted Answer

The answer of Which of the following is often selected...

Question 15

Which type of comparison group is commonly used in occupational studies of mortality because these data are quite accessible to researchers?

Accepted Answer

The general population is commonly used as a comparison group in occupational studies of mortality because data on the general population's mortality rates are readily accessible and can be used to compare with the occupational group being studied.

Question 16

Epidemiologists have found that which type of comparison group is the best type of comparison group to use in a cohort study?

Accepted Answer

An internal comparison group, which consists of unexposed members of the same cohort, is often the best choice because it is more likely to be similar to the exposed group in terms of confounding variables.

Question 17

If lost individuals are more or less likely to be exposed than those successfully traced, the study results may suffer from which of the following?

Accepted Answer

Selection bias occurs when there is a systematic difference in characteristics between those who are included in the study and those who are not, potentially affecting the study's validity.

Question 18

Observational studies are considered "natural" experiments because the investigator acts as a disinterested observer, merely letting nature take its course.

Accepted Answer

Observational studies do not involve manipulation by the researcher; instead, they observe and analyze outcomes in natural settings without intervention.

Question 19

The timing of prospective cohort studies is similar to that of experimental studies?

Accepted Answer

Prospective cohort studies and experimental studies both follow participants over time to observe outcomes, although cohort studies do not involve intervention by the researchers.

Question 20

Investigators in a retrospective cohort study can usually obtain more detailed information on exposures and other key variables because they have more control of the data collection process and can gather information directly from the participants.

Accepted Answer

In a retrospective cohort study, investigators rely on existing records and data, which limits their control over data collection and the level of detail available.

Quiz 8: Cohort Studies