Chapter 3 - THREE CLAIMS, FOUR VALIDITIES: INTERROGATION TOOLS FOR CONSUMERS OF RESEARCH

Variable

An attribute that varies, having at least two levels, or values. See also dependent variable

Level

One of the possible variations, or values, of a variable. Also called condition.

Constant

An attribute that could potentially vary but that has only one level in the study in question.

Measured Variable

A variable in a study whose levels (values) are observed and recorded.

Mainpulated Variable

A variable in an experiment that a researcher controls, such as by assigning participants to its different levels (values).

Conceptual Variable

A variable of interest, stated at an abstract, or conversational, level. Also called construct.

Construct

A variable of interest, stated at an abstract level, usually defined as part of a formal statement of a psychological theory.

Conceptual Definition

A researcher's definition of a variable at the theoretical level. Also called construct.

Operational Definition

The specific way in which a concept of interest is measured or manipulated as a variable in a study. Also called operationalization or operational variable.

Operational Variable

The specific way in which a concept of interest is measured or manipulated as a variable in a study. Also called operationalization or operational definition.

Operationalize

To turn a conceptual definition of a variable into a specific measured variable or manipulated variable in order to conduct a research study.

Claim

The argument a journalist, researcher, or scientist is trying to make.

Frequency Claim

A claim that describes a particular rate or degree of a single variable.

Association Claim

A claim about two variables, in which the value (level) of one variable is said to vary systematically with the value of another variable.

Correlate

To occur or vary together (covary) systematically, as in the case of two variables

Correlational Study

A study that includes two or more variables, in which all of the variables are measured; can support an association claim.

Positive Association

An association in which high levels of one variable go with high levels of the other variable, and low levels of one variable go with low levels of the other variable. Also called positive correlation.

Scatterplot

A graphical representation of an association, in which each dot represents one participant in the study measured on two variables.

Negative Association

An association in which high levels of one variable go with low levels of the other variable, and vice versa. Also called inverse association, negative correlation.

Zero Association

A lack of systematic association between two variables. Also called zero correlation.

Causal Claim

A claim arguing that a specific change in one variable is responsible for influencing the value of another variable.

Validity

The appropriateness of a conclusion or decision.

Construct Validity

An indication of how well a variable was measured or manipulated in a study.

Generalizability

The extent to which the subjects in a study represent the populations they are intended to represent; how well the settings in a study represent other settings or contexts.

External Validity

An indication of how well the results of a study generalize to, or represent, individuals or contexts besides those in the study itself.

Statistical Validity

The extent to which statistical conclusions derived from a study are accurate and reasonable. Also called statistical conclusion validity.

Margin of Error of the Estimate

A statistic, based in part on sample size, indicating the probable true value of a percentage estimate in the population.

Type 1 Error

A "false positive" result in the statistical inference process, in which researchers conclude that there is an effect in a population, when there really is none.

Type 2 Error

A "miss" in the statistical inference process, in which researchers conclude that their study has not detected an effect in a population, when there really is one.

Covariance

The degree to which two variables go together. Also one of three criteria for establishing a causal claim, which states that, in a study's results, the proposed causal variable must vary systematically with changes in the proposed outcome variable

Temporal Preedence

One of three criteria for establishing a causal claim, stating that the proposed causal variable comes first in time, before the proposed outcome variable.

Internal Validity

One of three criteria for establishing a causal claim; a study's ability to rule out alternative explanations for a causal relationship between two variables.

Experiment

A study in which one variable is manipulated and the other is measured.

Independent Variable

In an experiment, a variable that is manipulated. In a multiple-regression analysis, a predictor variable used to explain variance in the criterion variable.

Dependent Variable

In an experiment, the variable that is measured. In a multiple-regression analysis, the single outcome, or criterion variable, the researchers are most interested in understanding or predicting. Also called outcome variable.

Random Assignment

The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups.