Research methods: hypotheses, variables and designs

Hypotheses and variables

• An aim is a general statement of what a study will investigate. A hypothesis is a testable prediction.
• An alternative (experimental) hypothesis predicts a difference or relationship; a null hypothesis predicts no difference or relationship.
• The independent variable (IV) is what the researcher changes; the dependent variable (DV) is what is measured.
• Extraneous variables are other factors that might affect the DV; they should be controlled.

Experimental designs

• Independent groups: different participants in each condition. There are no order effects, but participant differences may affect results.
• Repeated measures: the same participants do all conditions. Participant differences are controlled, but order effects (practice or fatigue) can happen; counterbalancing reduces them.
• Matched pairs: participants are matched on key features, then one of each pair goes into each condition.

Types of research method

• Laboratory experiments: controlled conditions, but can be artificial. Field experiments: in a natural setting, more realistic but less control. Natural experiments: the IV occurs naturally.
• Interviews (structured or unstructured), questionnaires (open and closed questions), case studies (in-depth study of one person or group), observations, and correlational studies.

Key terms

Hypothesis

A testable prediction.

Null hypothesis

A prediction of no difference or relationship.

Independent variable

The variable the researcher changes.

Dependent variable

The variable the researcher measures.

Extraneous variable

Another variable that could affect the results.

Independent groups design

Different participants in each condition.

Repeated measures design

The same participants in every condition.

Counterbalancing

Varying the order of conditions to reduce order effects.