Variables

What does operationalising variables mean?

Operationalising variables means clearly describing the variables (IV and DV) in terms of:

• How they will be manipulated (IV)

• How they will be measured (DV)

What is the independent variable?

The independent variable is the variable that the experimenter manipulates (changes).

What is the dependent variable?

The dependent variable is the variable that is measured to tell you the outcome.

What is an extraneous variable?

An extraneous variable is any variable that, if not controlled, may:

• Affect the DV

• Give a false impression that the IV has produced changes, when it has not

What is a confounding variable?

A confounding variable is an extraneous variable that varies systematically with the IV, meaning:

• We cannot be sure of the true source of the change in the DV

Where are covariables studied?

Covariables are studied in correlations.

What are order effects?

Order effects occur in a repeated measures design and refer to how the positioning of tasks influences the outcome.

Examples include:

• Practice effect (performance improves on second task)

• Boredom/fatigue effect (performance worsens on second task)

How can order effects be controlled?

Using counterbalancing:

• A way of controlling order effects in a repeated measures design

• e.g. Half the participants do condition A → B, the other half do B → A

What are participant variables?

Participant variables occur when participants in one group differ in a significant way from participants in another group, which may affect the DV.

How can participant variables be controlled?

• Random allocation → participants are randomly assigned to groups

• Matched pairs design → participants matched on key characteristics

What are situational variables?

Situational variables are factors in the environment that may affect the DV.

How can situational variables be controlled?

By using a standardised procedure (e.g. same environment, instructions, and conditions for all participants).

What are investigator effects?

Investigator effects result from the effects of a researcher’s behaviour and characteristics on an investigation.

How can investigator effects be controlled?

• Double blind control →

  • Participants are not told the true purpose

  • Experimenter is also blind to at least some aspects of the design

• Standardised instructions and/or procedures

What are demand characteristics?

Demand characteristics occur when participants:

• Try to make sense of the research situation

• Try to guess the purpose of the study

• Try to present themselves in a good way

How can demand characteristics be controlled?

• Double blind control (participants and researcher unaware of key aspects)

• Single blind control → participants are not told the true purpose of the research

Why is controlling extraneous variables important?

Because it ensures that changes in the DV are due to the IV, increasing the validity of the study and avoiding confounding variables.