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Experiments in Research

Research methods designed to establish cause-and-effect relationships between variables.

The Experimental Method

Establishing Causality

Experiments are research methods designed to establish cause-and-effect relationships between variables. The key feature is the manipulation of an independent variable (IV) to observe its effect on a dependent variable (DV), while controlling for extraneous variables that might influence the results.

Key Experimental Designs

Understanding the context and control level defines the experimental type.

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Laboratory Experiment

Highly controlled environment, maximizes internal validity.
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Field Experiment

Conducted in a natural setting; IV manipulated by researcher.
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Quasi-Experiment

IV is naturally occurring (pre-existing groups); no random allocation.
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Replicability

The ability to reproduce the exact conditions and verify results.

Laboratory Experiment Analysis

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The Pros (High Control) High control over extraneous variables; cause-and-effect reliably established; high replicability which verifies results.
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The Cons (Low Validity) Artificial settings threaten ecological validity; participants might guess the aims (demand characteristics).

Field Experiment Features

This design balances manipulation with realism, but sacrifices control.

1

Setting & Validity

Conducted in a natural setting; high ecological validity because participants act naturally.
2

Causality

Since the IV is manipulated, cause-and-effect conclusions can still be drawn.
3

Challenges

Less control over extraneous variables; replication is more difficult.
4

Ethical Concerns

Consent and privacy are challenging since participants might not know they are being studied.

Quasi-Experiment Rationale

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Core Constraint: Quasi-experiments are essential when the independent variable is naturally occurring (e.g., day vs. night shift workers) or a characteristic (e.g., disabled vs. non-disabled), making random allocation impossible or unethical.

Strengths and Weaknesses In General

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General Strengths Allow determination of cause-effect relationships, control of variables, replication is possible, high internal validity (especially for lab experiments).
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General Weaknesses Artificiality in lab experiments limits ecological validity; quasi-experiments can’t definitively establish causality; ethical considerations such as deception and informed consent.

Design Comparison Matrix

Comparing three experiment types on key methodological features.

Type Setting Control IV Manip. Random Alloc. Internal Validity Causality Est.
Lab Artificial High Yes Yes High Reliable
Field Natural Medium Yes Yes Medium Reliable
Quasi Natural Low No No Low Difficult
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Experiments Deck
Q
Main Purpose

What is the main purpose of an experiment?

A
Answer

To establish cause-and-effect relationships between variables.

Q
Independent Variable (IV)

What is the independent variable (IV) in an experiment?

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Answer

The variable that is manipulated to observe its effect.

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Dependent Variable (DV)

What is the dependent variable (DV)?

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Answer

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

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Laboratory Experiment

What distinguishes a laboratory experiment?

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Answer

High control over variables in a controlled, artificial environment.

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Drawback of Laboratory Experiments

What is a drawback of laboratory experiments?

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Answer

Artificiality can reduce ecological validity.

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Field Experiments

How do field experiments differ from laboratory experiments?

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Answer

Field experiments are conducted in natural settings with less control.

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Demand Characteristics in Field Experiments

Why might demand characteristics be lower in field experiments?

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Answer

Participants often don't know they are part of the study.

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Quasi-Experiments

What are quasi-experiments?

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Answer

Studies comparing pre-existing groups without random assignment.

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Causality in Quasi-Experiments

Why is it harder to establish causality in quasi-experiments?

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Answer

No random allocation and less control over confounding variables.

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Strength of All Experiments

What is a strength common to all experiments?

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Answer

Ability to determine cause-and-effect relationships.

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Ethical Concern

What is a key ethical concern in experiments?

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Answer

Deception and informed consent.

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Replicability

Why is replicability important for experiments?

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Answer

Verifying and confirming results through repetition.

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🧪 Experiments Quiz

1. Which type of experiment offers the greatest control over extraneous variables?

Laboratory experiments occur in controlled environments, allowing manipulation and control of variables.

2. Which of the following is a key feature of a quasi-experiment?

Quasi-experiments compare groups that pre-exist or conditions naturally occurring, without random assignment.

3. Field experiments have higher ecological validity than laboratory experiments. (True or False)

Field experiments take place in natural settings where participants behave normally.

4. Demand characteristics are least likely to affect which type of experiment?

Because participants often do not know they are being studied during field experiments, demand characteristics are reduced.

5. Why is replicability more difficult in field experiments compared to laboratory experiments? (Short Answer)

Because field experiments have less control over external variables that cannot be perfectly duplicated in subsequent studies.

📊 Results

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