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Experimental Methods in Psychology

Foundations of Psychological Research

What are Experimental Methods?

Experimental methods are a core approach in psychology used to investigate cause-and-effect relationships by manipulating one or more variables and observing their effects on other variables. Understanding experimental design and related concepts is essential for evaluating and conducting psychological research.

Key Concepts: The Variables

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Independent Variable (IV)

The variable that the researcher manipulates to see if it causes a change.
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Dependent Variable (DV)

The outcome affected by changes in the IV; what the researcher measures.
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Operationalisation

Clearly defining variables in measurable terms (e.g., 'sleep' defined as 'number of hours slept').
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Extraneous Variables

Variables other than the IV that could affect the DV. When uncontrolled, they become confounding.

Types of Experimental Design

These three types differentiate based on the level of control over the environment and the independent variable.

1

Laboratory Experiments

Conducted in controlled settings where the IV is manipulated and extraneous variables controlled. Offer high internal validity but may lack ecological validity (applicability to real-world settings).
2

Field Experiments

Conducted in everyday environments outside the laboratory. They maintain some control over the IV while increasing ecological validity but with less control over extraneous variables.
3

Natural Experiments

The IV is not manipulated by the researcher but varies naturally (e.g., studying effects of natural disasters). Researchers observe effects but cannot establish causality as confidently.

Experimental Design Variations

The method of assigning participants to conditions determines the design variations used below.

I

Independent Groups Design

Different participants are assigned to each condition. Advantages: No order effects or practice effects; Disadvantages: differences between groups may affect results (participant variables).
R

Repeated Measures Design

The same participants take part in all conditions. Advantages: Controls participant variables, needs fewer participants; Disadvantages: risk of order effects, which can be controlled through counterbalancing.
M

Matched Pairs Design

Participants are paired based on key characteristics, and each member of the pair is assigned to different conditions. This controls for participant variables but is time-consuming and difficult to match perfectly.

Controlling Extraneous Variables

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Ensuring Research Validity: Ensuring research validity means controlling variables that could confound results. Key methods include Standardisation, Blinding (single/double), and Random allocation to reduce systematic bias.

Strengths vs. Limitations

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The Strengths Establishing Causality: By manipulating the IV and controlling extraneous factors, experiments allow researchers to draw cause-and-effect conclusions. High Control and easy Replication due to standardized procedures.
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The Limitations Artificiality: Lab experiments often lack ecological validity. Other limitations include Ethical Constraints, Demand Characteristics, and Order Effects (in repeated measures designs).

Ethical Considerations

Researchers must adhere to strict guidelines to protect the welfare and rights of participants.

1

Informed Consent

Participants must agree to take part, knowing what the experiment involves (except in some covert behavior studies).
2

Right to Withdraw

Participants can leave at any point without penalty.
3

Protection from Harm

Ensuring no physical or psychological harm.
4

Debriefing

Informing participants about the aim and deception (if used) after the experiment.

Quantitative Data and Analysis

Mean, Median, Mode, Standard Deviation
Experiments generate numerical data for the DV, which can be statistically analyzed to determine if differences between experimental conditions are significant. Measures of central tendency, dispersion, and significance tests (e.g., t-tests) are common tools.
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Experimental Methods in Psychology Deck
Term
Independent Variable (IV)

What is an independent variable (IV)?

Answer
Definition

The variable that the researcher manipulates to test its effect on the dependent variable.

Term
Dependent Variable (DV)

What is a dependent variable (DV)?

Answer
Definition

The variable that is measured to see the effect of changes in the IV.

Term
Experimental Hypothesis

Define experimental hypothesis.

Answer
Definition

A clear, testable prediction about how the IV will affect the DV.

Term
Operationalisation

What does operationalisation of variables mean?

Answer
Definition

Defining variables in measurable, specific terms.

Term
Control Variables

Why are control variables important?

Answer
Importance

They are kept constant to prevent influencing the DV and confounding results.

Term
Extraneous Variables

What are extraneous variables?

Answer
Definition

Variables other than the IV that may affect the DV and reduce internal validity if uncontrolled.

Term
Randomisation

What is randomisation in experiments?

Answer
Definition

Randomly assigning participants to conditions to reduce bias.

Term
Experimental Designs

Name the three main types of experimental designs.

Answer
Types

Laboratory, Field, and Natural experiments.

Term
Independent Groups Design

What is an independent groups design?

Answer
Definition

Different participants are assigned to each experimental condition.

Term
Repeated Measures Design

What is a repeated measures design?

Answer
Definition

The same participants take part in all conditions.

Term
Matched Pairs Design

Describe matched pairs design.

Answer
Definition

Participants are paired based on characteristics, then split into different conditions.

Term
Counterbalancing

What is counterbalancing?

Answer
Definition

A technique to control order effects in repeated measures designs by varying the order of conditions.

Term
Standardisation

How does standardisation help experiments?

Answer
Definition

It reduces variability by using the same procedures and instructions for all participants.

Term
Blinding

What is blinding in experiments?

Answer
Definition

Procedures that prevent participants or experimenters from knowing which condition participants are in to reduce bias.

Term
Strength of Experimental Methods

List one strength of experimental methods.

Answer
Strength

Ability to establish cause-and-effect relationships.

Term
Limitation of Experimental Methods

Name one limitation of experimental methods.

Answer
Limitation

Artificiality, limiting ecological validity.

Term
Ethical Considerations

What ethical considerations must be followed in experiments?

Answer
Considerations

Informed consent, right to withdraw, protection from harm, and debriefing.

Term
Data Type

What type of data do experiments typically generate?

Answer
Data

Quantitative, numerical data for statistical analysis.

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🧪 Experimental Methods in Psychology Quiz

1. What is the independent variable in an experiment?

The independent variable is the one changed by the experimenter to observe its effect on the dependent variable.

2. Which experimental design involves the same participants in all conditions?

In repeated measures design, each participant experiences every condition, allowing control over participant variables.

3. In a laboratory experiment, ecological validity is generally high. (True/False)

Laboratory experiments often have low ecological validity due to artificial settings.

4. Which method helps prevent participants from guessing the hypothesis and changing their behavior?

Blinding hides the condition details to reduce demand characteristics and bias.

5. What is the purpose of operationalising variables in an experiment?

To define variables in clear, measurable terms to ensure consistency and replicability.

📊 Results

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