Chapter 3: Variables, Research Questions, and Hypotheses

variable

• a characteristic that changes or varies

• NOT: the subjects (ex. pts) being studied; something that maintains the same value

dependent variable

measured to see whether the treatment or manipulation of independent variable had an effect (outcome, results, criterion variable)

independent variable

manipulated to examine its impact on a dependent variable (treatment, factor, predictor)

control variable

related to the dependent variable, the influence of which needs to be removed (restricting variable)

extraneous variable

related to the dependent variable or independent variable that is not part of the experiment (threatening variable)

confounding variable

extraneous variable that confounds the relationship between the variables (confounding variables)

do correlational studies have independent variables?

no (since not cause and effect)

hypothesis

• predicted answer to a research question

• describes predicted relationship between variables

  • causal relationship

  • association (non-causal)

• expressed in words or mathematically

null hypothesis

statement of equality

• ex. status quo, no association, no causal relationship, no difference between groups

alternative/research hypthesis

statement of inequality

• ex. an association, a causal relationship, a difference between group

directional hypotheses

shows the direction of the relationship or difference (mathematically expressed with less than (<) or greater than (>) symbols

non-directional hypotheses

does not show the direction of the relationship or difference (mathematically expressed with an not equal to symbol (≠))