Observational Study Designs

Question 1

what are major categories of quantitative designs?

Answer 1

non experimental
pre experimental
quasi experimental
true experimental

Question 2

what are non-experimental designs?

Answer 2

methodologies where the researcher observes and analyzes naturally occurring situations without intervening or manipulating variables. Instead of actively changing variables, researchers simply observe and gather data from existing conditions.

Question 3

what are types of non experimental designs?

Answer 3

survey designs
passive observation
ex post facto design

Question 4

what are survey used for?

Answer 4

describe
compare
explain

Question 5

what is a cross sectional study design?

Answer 5

is like taking a snapshot of a group of people or things at one specific point in time. It involves collecting data from a group of participants at a single time point to understand characteristics, behaviors, or conditions.

Question 6

what is prevalence?

Answer 6

existing cases/ number sampled

Question 7

what are the strengths of a cross sectional study?

Answer 7

quick
inexpensive
useful for public health planning, evaluating, and monitoring
helps determine association between variable

Question 8

what are weaknesses of cross sectional studies?

Answer 8

cannot establish cause and effect
temporality
prone to selection bias
rare diseases or rapidly fatal disease = difficult sampling

Question 9

what is a case control study design?

Answer 9

like detective work to understand the causes of a particular outcome, like a disease. Researchers start by identifying people with the outcome (cases) and people without it (controls). Then they look back in time to compare the two groups, trying to find out what might have caused the outcome.

Question 10

what are the requirements for the control subjects in a case-control study?

Answer 10

need to be similar on all variables except the exposure and outcome

must be at similar risk of developing the outcome

case and controls must arise from the same population

Question 11

what are common sources of bias in case-control studies?

Answer 11

recall bias: cases and controls may recall past exposure differently

interviewer/observer bias: the recording of exposure information may vary depending on the investigators knowledge of an individuals disease status

selection bias: controls are unrepresentative of the population that produces the cases

Question 12

what makes a good case control study?

Answer 12

the right question

clear distinction between cases and controls

sampling frame and strategy

collecting data for cases and controls in the same way

blind the assessor

Question 13

what are some strengths of case-control studies?

Answer 13

inexpensive

efficient for rare diseases

good to study conditions that would be unethical to expose the participatnts

Question 14

what are weakness of case-control studies?

Answer 14

finding out past exposures can be difficult

subject to bias

selection of controls can be difficult

Question 15

what is the odds ratio used to estimate?

Answer 15

the strength of the association between exposure and outcome

Question 16

what is a cohort study design?

Answer 16

like following a group of people over time to see how their lives unfold. Researchers gather a group of individuals who share a common characteristic or experience Then, they observe and collect data from this group over a period of time, tracking their outcomes and exposures.

Question 17

is a cohort study prospective or retrospective?

Answer 17

it can be both!

Question 18

what is the best design for determining the incidence and natural history of a condition?

Answer 18

cohort study

Question 19

what is prospective cohort study?

Answer 19

A group of people is chosen who do not have the outcome of interest (e.g., stroke).

• The investigator then measures a variety of variables that might be relevant to the development of the condition.
• Over a period of time the people in the sample are observed to see whether they develop the outcome of interest (stroke).

Question 20

what is a retrospective cohort study?

Answer 20

These use data already collected for other purposes.

• The methodology is the same but the study is performed post-hoc.
• The cohort is “followed up” retrospectively.
• The study period may be many years but the time to complete the study is only as long as it takes to collate and analyze the data.

Question 21

what are some strengths of a cohort design?

Answer 21

good for studying rare exposures

can establish temporal sequence

can yield incidence (the # of new cases that develop during a specified time)

Question 22

what are some weaknesses of cohort studies?

Answer 22

loss of some subjects to follow up can affect the outcome

very expensive

source of recall, selection, confounding bias