Logic of Experiments

A collection of vocabulary flashcards summarizing key terms and concepts related to the logic and structure of experiments.

Treatment or Independent Variable

The treatment or manipulation in an experiment that is tested to observe its effect.

Outcome or Dependent Variable

The outcome or measurement that is affected by the independent variable.

Experimental Group

The group that receives the treatment in an experiment.

Control Group

The group that does not receive the treatment in an experiment.

Pretest

The measurement of the dependent variable before the introduction of the treatment.

Posttest

The measurement of the dependent variable after the treatment has been introduced.

Random Assignment (selection subject)

A method for randomly distributing subjects into experimental and control groups to ensure equivalency. A method for assigning cases to groups (experimental and control groups) for purposes of making comparison

Matching (selecting subjects)

A procedure for pairing subjects based on similar characteristics for better comparison. Matching cases in groups example pairing person on the bias of similarities of gender, age, years in school, or some other characteristics

Double-Blind Experiment

An experimental design in which neither the subjects nor the experimenters know which group the subjects are assigned to.

Classical Experimental Design

An experimental setup that includes pretest and posttest, an experimental group, a control group, and random assignment.

Solomon Four-Group Design

An experimental design that includes two experimental groups and two control groups, with and without pretests.

Internal Validity

The extent to which the treatment is the true causal factor producing change in the dependent variable.

Selection Bias

A threat to internal validity that occurs when subjects are not randomly assigned, leading to inequivalent groups.

History

An event unrelated to the treatment will occur during the experiment and influence the outcome.

Maturation

Some biological, psicológico or emotional process within the subject has occurred.

testing

Princess measures me influenced the outcome (example looking at the test one time then you take it again you can used to it.)

Instrumentation

Changes in measuring instruments or observers that may influence the outcome of an experiment.(example your observing)

statistical regression

problem of extreme values. (Example your subject are violet criminals watch violet videos but they don’t become aggressive because of their values)

Mortality

When subjects drop out of an experiment before it is completed. (You lose subjects)

Contamination

When subjects in different groups communicate with each other and learn about the other's treatments.

External Validity

The ability to generalize experimental findings to settings and populations beyond the experiment.

realism

Subjects are car up in the experiment and are truly influenced by it. (this is desirable because we want to subject to be influenced by the treatment. Researchers will attempt to create realistic condition so that the subject will be truly Influenced.)

Reactivity

The phenomenon where subjects alter their behavior due to the awareness of being observed.(subjects may react differently in an experiment then they would be in real life.)

Hawthorne effect

React to the attention received From The Experimenter

demand characteristics

Subjects pick up clues about true hypothesis and may add according to what is demanding of them.

Placebo effect

Subject are given the place post but respond as they have received the real treatment

Field experiments

Experiment conducted in a natural setting. Higher external validity, but lower interno validity.

strength of experiments

Make valid casual insurance experiments are very effective in determining cause an effect. 2. replicate a given experiment: it is easy to replicate or Repeat Someone else’s experiment)

weaknesses of an experiment

Artifacts and removed from your life situations(this is specifically True With The Life Experiments) include volunteers