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Match the study type with the appropriate example
| Study Types |
|
Examples |
| 1. double-blinded randomized clinical trial |
|
A. A researcher identifies a group of subjects who just
made the decision to begin using birth control pills and
another group of subjects who decided not to use birth
control pills. The researcher observes both groups over a
period of time to determine whether one group develops a
higher cancer incidence than the other. |
| 2. single-blinded randomized clinical trial |
|
B. A researcher compares the medical records of women who
used a contemporary form of birth control pills for 10+ years
with the medical records of women who used a type of birth
control previously available for 10+ years. The researcher
compares cancer incidence between the two groups. |
| 3. case series |
|
C. A researcher identifies a group of individuals with a
rare auto-immune disease. The researcher looks back in time
to determine how many of the subjects grew up in homes that
had asbestos siding. |
| 4. concurrent cohort |
|
D. A researcher identifies a group of individuals with
Type I diabetes and another without diabetes. The researcher
identifies genetic differences between the two groups. |
| 5. historical cohort |
|
E. A homogenous group of subjects is identified and
randomly assigned to two separate groups. One group is
administered a stimulant and the other is administered a
placebo. Then both groups undergo an IQ test. The
investigator is aware of which group received the stimulant,
but the subjects are not. |
| 6. case-control |
|
F. A homogenous group of subjects is identified and
randomly assigned to two separate groups. One group receives
the Pneumococcal vaccine and the other receives a placebo.
Neither the researcher nor the subjects is aware of which is
the study and control groups. The researcher records
incidence of ear infections (otitis media) for one year. |
| 7. cross-sectional case-control |
|
G. A researcher identifies a group of individuals with
chronic lower back pain and another group free of lower back
pain. The researcher compares the body mass index of the two
groups. |
Definitions
- Double-blinded randomized clinical trials
- Random assignment of subjects to two groups. Neither
investigator nor subjects are aware of assignments. An
intervention is administered to only one group.
- Single-blinded randomized clinical trials
- Random assignments of subjects to two groups. Only
investigator is aware of assignments. An intervention is
administered to only one group.
- Case series (aka descriptive studies or time series)
- One person or group of subjects receives an intervention.
No formal control group exists but a historical control or
prior experience may be used for comparison.
- Concurrent cohort study
- One group of subjects has decided on their own to use an
intervention. Comparison is made with another group of subjects
that decided on their own not to use the intervention or to use
a different intervention. Both groups partake in the study
simultaneously and are observed forward in time.
- Historical cohort (aka retrospective cohort)
- One group of subjects has decided on their own to use an
intervention. Comparison is made with another group of subjects
that decided on their own not to use the intervention. The two
groups exist at different periods in time.
- Case-control study (aka retrospective study)
- Two groups of subject are identified, one which has
developed a disease and the other which has not. The researcher
looks back in time to identify factors that might have caused
the disease.
- Cross-sectional study (aka cross-sectional case-control
study)
- Two groups of subjects are identified, one which has
developed a disease and the other which has not. The cause of
the disease is presently affecting the subjects at the time of
study.
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