Observational Studies, Researchers observe or question the participants about opinions, behaviors, or outcomes.
Experiments, researchers manipulate something and measure the effect of the manipulation on some outcome of interest., Randomized experiments, experiments in which the participants are randomly assigned to participate in one condition or another
Unit: Used to indicate a single individual or object being measured., Experimental Unit: The most basic entity to which different treatments can be assigned.
Subjects: When the experimental units are people
Participants: In experiments and observational studies, subjects may also be called participants
Explanatory variable is one that may explain or may cause differences in a response variable.
Response variable can also be known as an outcome or dependent variable., dependent variable: the values are sometimes thought to depend on the values of the explanatory variable.
Explanatory variables can also be known as independent variables
Confounding variable: a variable that both affects the response variable and also is related to the explanatory variable
Lurking Variable: describes a potential confounding variable that is not measured and is not considered in the interpretation of the study.
Control groups: treated identically in all respects except they don't receive the active treatment
Placebos: A placebo looks like the real drug but has no active ingredient, Placebo effect: so strong that most drug research is done by randomly giving half the participants a placebo instead of the drug.
Blinding, Double-blind: neither the participant nor the researcher taking the measurements knows who had which treatment, Single-blind: the participants do not know which treatment they have been assigned
Matched-pair designs: experimental designs that use either two matched individuals or the same individual to receive each of two treatments
Blocks: experimental units are divided into homogeneous groups
Completely Randomized design: If treatments are randomly assigned to experimental units without using matched pairs or blocks
Matched-pair design: When matched pairs are used
Randomized block design: When blocks are used
Retrospective: The data is from the past
Prospective: follow participants into the future and record relevant events and variables
Case-control study: cases who have a particular attribute or condition are compared to controls who do not
Hawthorne: participants in an experiments respond differently than they otherwise would, just because they are in an experiment
Experimenter: Numerous ways in which the experimenter can bias the results