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Variables, Their Roles, and Operationalisation

Research Planning Foundation

Core Context

A crucial element in planning and conducting research is understanding variables, their roles, and how to measure them clearly through operationalisation. We begin by defining the two primary variables that govern experimental design.

Primary Variable Types

These variables define the cause-and-effect relationship being investigated in the research.

⚙️

Independent Variable (IV)

The variable manipulated or changed by the researcher to observe its effect. Example: "amount of sleep."
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Dependent Variable (DV)

The variable measured to assess the effect of the IV. Example: "reaction time measured in milliseconds."

Note: Precisely defining the IV ensures that the manipulation is clear and reproducible. The DV must be measurable and sensitive to changes in the IV.

Operationalisation Examples

Operationalisation involves defining variables in concrete, measurable terms. This removes subjectivity and improves clarity.

1

Instead of "Aggression"

"number of times a participant presses a button in a hostile task."
2

Instead of "Intelligence"

"score on an IQ test."

Key Principle of Measurement

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Operationalisation is essential: Clear operational definitions are necessary to reduce ambiguity and increase reliability and validity of measurement, crucial for replication.

Extraneous vs. Confounding

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Extraneous Variables Controlled If controlled, they remain extraneous. They are all variables other than the IV that might affect the DV.
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Extraneous Variables Uncontrolled (Confounding) If not controlled, they become confounding variables, which threaten internal validity and harm the credibility of results.

Control Strategies

Strategies implemented to ensure internal validity by reducing the influence of unwanted variation.

I

Randomisation

Using chance to assign participants to conditions to evenly distribute extraneous variables.
II

Standardisation

Keeping procedures the same for all participants reduces variation (e.g., identical testing environment, instructions).
III

Counterbalancing

In repeated measures designs, to control order effects.
IV

Matching

As in matched participants design, to reduce participant variable effects.
Variables, Their Roles, and Operationalisation
Q
Independent Variable (IV)

What is an independent variable (IV)?

A
Definition

The variable manipulated by the researcher to observe its effect on the dependent variable.

Q
Characteristic of IV

What is a characteristic of the independent variable?

A
Feature

It must have at least two conditions or levels.

Q
Dependent Variable (DV)

What is the dependent variable (DV)?

A
Definition

The variable measured to assess the effect of the independent variable.

Q
DV Requirements

Why must the dependent variable be measurable and sensitive?

A
Reason

To accurately detect changes resulting from manipulation of the IV.

Q
Operationalisation

What does operationalisation of a variable involve?

A
Explanation

Defining variables in concrete, measurable terms to remove subjectivity.

Q
Example of Operationalisation

Give an example of operationalisation for "aggression."

A
Example

Number of times a participant presses a button in a hostile task.

Q
Extraneous Variables

What are extraneous variables?

A
Definition

Variables other than the IV that might affect the DV.

Q
Confounding Variable

What is a confounding variable?

A
Definition

An extraneous variable that influences the DV, threatening validity.

Q
Controlling Extraneous Variables

Name one strategy to control extraneous variables.

A
Examples

Randomisation, standardisation, counterbalancing, holding variables constant, or matching.

Q
Importance of Control

Why is controlling extraneous variables important?

A
Reason

To maintain internal validity and ensure accurate results.

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📊 Research Methods Quiz

1. What is the role of the independent variable (IV) in research?

The IV is the variable that researchers manipulate to observe effects on the DV.

2. Which of the following is an example of operationalisation?

Operationalisation provides clear, measurable definitions rather than vague concepts.

3. Why must the dependent variable (DV) be measurable and sensitive?

The DV measures the effect of the IV, so it must accurately reflect changes.

4. Which strategy helps reduce the influence of extraneous variables in a repeated measures design?

Counterbalancing controls order effects by varying the sequence of conditions.

5. What can happen if extraneous variables are not controlled?

Extraneous variables can confound results, reducing internal validity.

📊 Results

  • Notes and Quiz
  • Psychology
  • A Level
  • Research Methods
  • OCR