Experiments and Observational Studies Flashcards
A study based on data in which no manipulation of factors has been employed.
Observational Study
An observational study in which subjects are selected and then their previous conditions or behaviors are determined.
Retrospective Study
An observational study in which subjects are followed to observe the future outcomes. Not an experiment because no treatments are deliberately applied.
Prospective Study
To be valid, an experiment must do this when assigning experimental units to treatment groups.
Random Assignment
A variable whose levels are manipulated by the experimenter.
Factor
A variable whose values are compared across different treatments.
Response Variable
This manipulates factor levels to create treatments, randomly assigns subjects to these treatment levels, and then compares the response of the subject groups across treatment levels.
Experiment
The individuals who participate in an experiment, especially when they are human.
Subjects or participants
Individuals on whom an experiment is performed.
Experimental Unit
The specific values that the experimenter chooses for a factor.
Levels
The process, intervention, or other controlled circumstance applied to randomly assigned experimental units.
Treatment
Control
Randomize
Replicate
Block
4 Principles of Experimental Design
Do this to aspects of the experiment that we know may have an effect on the response, but that are not the factors being studied.
Control
Do this to subjects of treatments to even out effects that we cannot control
Randomize
Do this over as many subjects as possible.
Replicate
Do this to reduce the effects of identifiable attributes of the subjects that cannot be controlled.
Block
When this is done, all experimental units have an equal chance of receiving any treatment.
Completely Randomized Design
When a observed difference is too large for us to believe that it is likely to have occurred naturally:
Statistically Significant
The experimental units assigned to a baseline treatment level typically either the default treatment or a null, placebo treatment.
Control Group
Any individual with an experiment who is not aware of how subjects have been allocated to treatment groups is this…
Blinded
When either those who could influence the results OR those who evaluate the results are not aware of how subjects have been allocated to treatment groups, the experiment is this:
Single-Blind
When either those who could influence the results AND those who evaluate the results are not aware of how subjects have been allocated to treatment groups, the experiment is this:
Double-Blind
A treatment known to have no effect, administered so that all groups experience the same conditions.
Placebo
The tendency of many human subjects (often 20% or more) to show a response even when administered a treatment known to have no effect.
Placebo Effect
