Research Designs

What are the comparison groups of a meta-analysis?

They vary by research question

What are the comparison groups of a RCT?

intervention vs. control

What are the comparison groups of Before-After studies?

non-concurrent comparison → after vs before the intervention

external control group → after vs before the intervention

What are the comparison groups of prospective cohort studies?

exposed group vs. unexposed group

What are the comparison groups of retrospective cohort studies?

exposed group vs. unexposed group

What are the comparison groups of multiple cohort studies?

exposed group vs. unexposed group

What are the comparison groups of case-control studies?

outcome vs no outcome

What are the comparison groups of nested case-control studies?

outcome vs no outcome

What are the comparison groups of case crossover designs?

compare exposures for cases at the time of the outcome with exposures for the same people at a different time period

What are the comparison groups of cross-sectional studies?

exposed group vs. unexposed group

What are the comparison groups of case series/case reports/case studies?

not applicable - may include findings from historical controls, but there is no formal concurrent control group)

What direction is the time component of a RCT?

Prospective

What direction is the time component of a before-after study?

varies

What direction is the time component of a prospective cohort study?

prospective

What direction is the time component of a retrospective cohort study?

retrospective

What direction is the time component of a multiple cohort study?

prospective OR retrospective

What direction is the time component of a case-control study?

retrospective

What direction is the time component of a nested case control study?

retrospective

Note: the data in the cohort study it is nested in was collected prospectively

What direction is the time component of a case crossover study?

retrospective (because they can only be initiated after onset of an outcome)

What direction is the time component of a cross-sectional study?

no time component

What direction is the time component of a case-series/case report/case study?

varies

Is the outcome present at the start of a RCT?

No

Is the outcome present at the start of a before-after study?

typically, for some participants

Is the outcome present at the start of a prospective cohort study?

no (consider whether inadvertent presence of the outcome is possible)

Is the outcome present at the start of a retrospective cohort study?

no (consider whether inadvertent presence of the outcome is possible)

Is the outcome present at the start of a multiple cohort study?

no (consider whether inadvertent presence of the outcome is possible)

Is the outcome present at the start of a case control study?

Yes

Is the outcome present at the start of a nested case control study?

Yes

Is the outcome present at the start of a case crossover study?

Yes

Is the outcome present at the start of a cross-sectional study?

Yes

Is the outcome present at the start of a case series/case report/case study?

depends on the question

What is the classic effect measure of a meta-analysis?

summary estimates

What is the classic effect measure of a RCT?

Relative Risk (RR)

What is the classic effect measure of a before-after study?

difference-in-differences (if there is an external control group)

What is the classic effect measure of a prospective cohort study?

incidence, RR

What is the classic effect measure of a retrospective cohort study?

incidence, RR

What is the classic effect measure of a multiple cohort study?

incidence, RR

What is the classic effect measure of a case-control study?

Odds Ratio (OR)

What is the classic effect measure of a nested case-control study?

Odds Ratio (OR)

What is the classic effect measure of a case-crossover study?

Odds Ratio (OR)

What are the classic effect measures of a cross-sectional study?

prevalence to describe the population and relative prevalence to infer cause and effect relationships between the variables.

What is the classic effect measure of a case series/case report/case study?

descriptive