CHAPTER 7: THE BASICS OF EXPERIMENTATION

• independent variable - the variable an experimenter intentionally manipulates.
• confounded - when the value of an extraneous variable systematically changes along with the independent variable.
• dependent variable - outcome measure uses to assess the change in behavior produced by the independent variable.
• operational definition - meaning of a variable in an experiment by defining it in terms of observable operations, procedures, and measurements.
• experimental operational definition - specifies the exact procedure for creating values of the independent variable.
• measured operational definition - specifies the exact procedure for measuring the dependent variable.
• nominal scale - categories that can be named using a shared feature
• ordinal scale - using ranks but does not assign precise values
• interval scale - using equal intervals between values with no absolute zero point
• ratio scale - using equal intervals between values and an absolute zero
• reliability - consistency of experimental operational definitions and measured operational definitions
• interrater reliablity - observers agree in their measurement of the behavior
• test-retest reliability - person's scores are consistent across two or more administrations of a measurement procedure
• interitem reliability -which different parts of an instrument that are designed to measure the same variable achieve consistent results.
• validity - operational definition accurately manipulates the independent variable or measures the dependent variable
• predictive validity - how accurately a measurement procedure predicts future performance
• content validity - how accurately a measurement procedure samples the content of the dependent variable
• internal validity - changes in the dependent variable across treatment conditions were due to the independent variable
• confounding - occurs when an extraneous variable systematically changes across the experimental conditions.
• history threat - when an event outside the experiment threatens internal validity by changing the dependent variable
• maturation threat - produced when physical or psychological changes in the subject threaten internal validity by changing the DV
• testing threat - occurs when prior exposure to measurement procedure affects performance on this measure during the experiment.
• instrumentation threat - occurs when changes in the measurement instrument or measuring procedure threatens internal validity.
• selection threat - when an individual differences are not balanced across treatment conditions by the assignment procedure
• subject mortality threat - subjects drop out of experimental conditions at different rates
• selection interactions - occurs when a selection threat combines with at least one other threat
• method selection - describes the participants, apparatus or materials, and procedure of the experiment.