Chapter 7 Research Methods

procedural confound

A confound that occurs in a laboratory experiment or quasi-experiment when a researcher mistakenly allows a second variable to vary along with a manipulated variable. See also environmental confound.

operational confound

A confound that occurs when a measure designed to assess a specific construct such as self-esteem, time pressure, or happiness inadvertently measures something else as well. Operational confounds are applicable to both experimental and nonexperimental research designs and are closely tied to the notion of operational definitions.

replication

A follow-up experiment that tests the idea behind the original experiment again—often by making use of different operational definitions of the independent and dependent measures and sometimes by testing the idea on a different kind of research participant (e.g., adults versus children).

manipulation check

A measure taken to see if participants in different experimental conditions truly experienced the different levels of the independent variable that the researcher hoped to manipulate.

Matching

A method of assigning participants to experimental conditions. Researchers who use matching try to identify similar individuals in order to place them in different conditions. This is done to gain some degree of comparability between experimental conditions (i.e., to minimize the chance of a person confound). This strategy is inferior to random assignment.

pilot test (pilot study)

A preliminary study or "practice study" conducted by researchers before they conduct the full-blown version of the study in which they are interested. Pilot tests often allow researchers to refine their experiments and/or hypotheses by revealing errors or problems in the design of the study.

interaction

A statistical term indicating that the effect of an independent variable on the dependent variable is different at different levels of another independent variable. The presence of an interaction means that one cannot make a simple, blanket statement about the independent and dependent variables in a factorial study. See also main effect.

random assignment

A technique for assigning participants to different conditions in an experiment. The use of random assignment means that every person in the study has an equal chance of being assigned to any of the conditions of the study. The use of random assignment makes it highly likely that the groups of participants in different experimental conditions are highly similar to one another.

random sampling (random selection)

A technique for deciding which participants in a population are selected for inclusion in a study. When true random sampling is used, every person in a population (e.g., American adults) has an equal chance of being selected into the study. The use of random sampling makes it highly likely that the participants who take part in an investigation are highly similar to the entire population of people from whom they were sampled.

experimental simulation

An experiment in which participants are randomly assigned to treatment conditions but are asked to play a specific role or act out a part rather than engaging in wholly natural behavior.

noise

An extraneous variable in an experiment that (a) influences the dependent variable but that (b) is evenly distributed across experimental conditions. This is a not a threat to validity, but it may decrease a researcher's ability to detect the effect in which he or she is more interested. Contrast with confound and artifact.

manipulation

Systematically varying the level of an independent variable in an experiment, with the goal of seeing whether doing so has any effect on the measured level of a dependent variable. Manipulation and random assignment are the two defining ingredients of the experimental method.

internal validity

The degree to which a research finding provides accurate or compelling information about causality. The degree to which changes in the independent variable in a particular study really do influence the dependent variable in the way suggested by the results of the study.

external validity

The degree to which a research finding provides an accurate description of what typically happens in the real world. The degree to which the observed relation between an independent and a dependent variable in a specific study applies to people, times, and settings not examined in the study of interest.

mundane realism

The degree to which the physical setting in an experiment is similar to the real-world setting(s) in which the experimenter's independent and dependent variables are most likely to operate. See also experimental realism.

experimental realism

The degree to which the subjective experiences of research participants are realistic or psychologically meaningful. Well-designed experiments can be high in experimental realism even when they bear little physical resemblance to the real world (e.g., participants can be made fearful or anxious by being convinced that they are about to receive electric shocks to their big toes). See also mundane realism.

semantic priming

The finding that people recognize most words more quickly than usual when they have just been exposed to words that have a similar meaning. For instance, people are usually able to identify the word "smile" more quickly than usual if they have just been exposed to the word "happy." Semantic priming also refers to the experimental procedures used to demonstrate this effect.