Internal Validity

Front 1

Internal Validity

Back 1

Internal Validity – extent to which changes in the DV can confidently be attributed to the influence of the IV rather than to the potential influence of confounding variables

Front 2

Experimental Control

Back 2

Experimental Control – occurs to the extent that experimenter is able to eliminate effects on the DV other than the effect of the IV

Front 3

Extraneous variables

Back 3

Extraneous variables - any variable that is not systematically manipulated in an experiment but that still may effect the behavior being observed (tends to increase within-group variability making it more difficult to find differences in experimental conditions on the DV) – reduces POWER!
a. examples: initial differences within groups (e.g., ability, mood, motivation) & differences in how experimenter treats participants or differences in how participants react to experimental setting)

Front 4

Confounding variables

Back 4

Confounding variables – variables other than the IV on which the participants in one condition differ systematically from those in another condition (results in inability to eliminate alternative explanations for findings)

Front 5

Control of extraneous variables

Back 5

Control of extraneous variables - one type of extraneous variable is initial within-group differences – produces random error & lowers power (INCREASES Type 2 errors) – goal is to reduce – can do so by using:

Front 6

Limited population design

Back 6

Limited population design – select participants from a limited (homogeneous) population (e.g., college students)

Front 7

Before-after research designs

Back 7

Before-after research designs – designs in which the dependent measure is assessed both prior to and after the experimental manipulation has occurred