Chapter 5: Experiments and Observational Studies Flashcards
explanatory variable
one that attempts to explain or is purported to cause (at least partially) differences in a response variable (sometimes called an outcome variable).
treatment
one or a combination of categories of the explanatory variable(s) assigned by the experimenter.
randomized experiment
we create differences in the explanatory variable
and then examine the results.
observational study
observes differences in the explanatory variable and then notice whether these are related to differences in the response variable.
interactions
An interaction occurs when the effect of one explanatory variable on the response variable depends on what’s happening with another explanatory variable.
experimental units
the smallest basic objects to which we can assign different treatments in a randomized experiment
observational units
the objects or people measured in any study.
participants/ subjects
commonly used when the observational units are people.
volunteers
the participants in studies
control groups
groups which are handled identically to the treatment group(s) in all respects, except that they don’t receive the active treatment.
placebo
A placebo looks like the real drug but has no active ingredients.
placebo effect
the effect where the placebo produces the same side effects as the drug for the mere fact that the patient taking the drug thinks that they are receiving an actual treatment
double-blind procedure/ experiment
A double-blind experiment is one in which neither the participant nor the researcher taking the measurements knows who had which treatment.
single-blind procedure/ experiment
A single-blind experiment is one in which only one of the two, the participant or the researcher taking the measurements, knows which treatment the participant was
assigned.
matched-pair designs
Experimental designs that use either two matched individuals or the same individual to receive each of two treatments
randomized block design/ block design
An extension of the matched-pair design to three or more treatments is called a randomized block design, or sometimes simply a block design.
repeated-measures designs
designs in which the same participants are measured repeatedly
ecological validity
the variables have been removed from their natural setting and are measured in the laboratory or in some other artificial setting. Thus, the results do not accurately reflect the impact of the variables in the real world or in everyday life.
case-control study
In such a study, “cases” who have a particular attribute or condition are compared with “controls” who do not.
retrospective studies
observational studies in which participants are asked to recall past events
prospective studies
observational studies in which participants are followed into the future and events are recorded