Research Methods - Chapter 2

Variable

A class of outcomes that can take on more than one value. Variables are what researchers study.

Sample

A representative portion of a population.

Factorial design

A research design in which more than one independent variable is studied in various combinations with others.

Nondirectional research hypothesis

A research hypothesis that posits an inequality (such as a difference between groups) but makes no suggestion of the direction of that difference (such as more than or less than).

Directional research hypothesis

A research hypothesis that posits an inequality between groups with direction to that difference (such as more than or less than).

Null hypothesis

A statement of equality between groups in an investigation. The null hypothesis serves as a starting point for observing the effects of the independent variable(s) on the dependent variable and as a benchmark for the comparison of chance versus significant differences between groups.

Research hypothesis

A statement of inequality between groups in an investigation. Research hypotheses suggest directional or nondirectional relationships between variables.

Independent variable

A variable controlled by the researcher in an attempt to test the effects on some outcome, the dependent variable. Independent variables are also known as treatment variables owing to their manipulation and exposure to groups and individuals at the discretion of the researcher.

Control variable

A variable that has a potential influence on the dependent variable.

Extraneous variable

A variable that has an unpredictable impact on the dependent variable.

Moderator variable

A variable that is related to the variables of interest masking the true relationship between the independent and dependent variables.

Measurement

Assignment of values to objects, events, or outcomes according to rules.

Significance level

The amount of risk one is willing to take that the null hypothesis is true even though it is rejected.

Statistical significance

The degree of risk you are willing to take that you will reject a null hypothesis when it is actually true.

Population

The entirety of some group.

Dependent variable

The outcome variable of research; dependent variables are observed for effects resulting from the influence of another factor, the independent variable(s).

Chance

The unassuming explanation for differences between groups that implies that the differences are accounted for by variables other than those being studied.

Confounding

When variables compete to explain the effects found in a study.