Experiments

Experiments

• A fundamental method in psychological research, designed to explore the relationship between cause and effect.

• They involve altering one factor to observe its impact on another.

Core components of experimental design

• Independent Variable (IV)

• Dependent Variable (DV)

• Control Variable

• Extraneous Variable

• Confounding Variable

Independent Variable (IV)

• This is the factor/variable that researchers deliberately change or manipulate to test its effect on another variable.

Dependent Variable (DV)

This is the factor/variable that is measured to see how it is influenced by changes in the independent variable.

Extraneous Variables

These are additional factors that could potentially affect the dependent variable.

Researchers aim to control or eliminate these to ensure the results are due to the independent variable alone.

The 4 types of extraneous variables

1.) Participant Variables

2.) Situational Variables

3.) Experimenter effects/bias

4.) Demand Characteristics

Confounding Variables

When extraneous variables are not controlled, they can become confounding variables, directly impacting the dependent variable and skewing the results.

Control Variables

Variables (extraneous) that are isolated and controlled/kept the same, in order to avoid them becoming confounding variables (and affecting the results)

Participant Variables

Extraneous variables specific to the participants of an investigation, for example their mood, ability or personality.

Situational variables

An extraneous variable present in the environment of the study

Demand Characteristics

when the participant alters their behaviour in response to the perceived aims of the investigation.

Standardised Procedure

where the procedure of a study is the same across all conditions.

Experimenter/Investigator effect/bias

When a researcher unintentionally gives clues to participant, altering their behavior

Order effects

Whe participants improve or worsen in the second condition because they have practiced or become fatigued

Preventing Demand Characteristics: Double-blind technique

When the aims of the study are withheld from both participants and researchers

Preventing Demand charactristics: Single-blind technique

When information about the study is withheld from participants only

Operationalisation

Making variables in an investigation detailed and specific

The 3 types of Experiments (Experimental Methods)

1.) Laboratory Experiment

2.) Field Experiment

3.) Quasi Experiment

Lab Experiment

The researcher manipulates an independent variable to measure its effect on a dependent variable; this is carried out in a carefully controlled (often artificial) environment which has been set up for the purpose of the research

Field Experiment

The researcher manipulates an independent variable to measure its effect on a dependent variable; this is carried out in a natural “real-world environment “

Quasi (Natural) Environment

The independent variable is naturally occurring meaning that groups of participants naturally fall into different conditions and this cannot be directly manipulated by the researcher

Strength of Lab experiments: Highly controlled

Participants are tested in consistent/ same environment so the results should have internal reliability

Strength of Lab experiments: Extraneous Variables

Extraneous Variables are identified and controlled so they cannot confound the results, improving internal validity, and demonstrating clearer cause and effect

Strength of Field Experiments: Ecological Validity

Ecol. Valid. Is good because it’s set in the participants natural environment. Therefore, the results are generalizable to explain the phenomenon in its real-world setting.

Strength of Field experiments: Less Experimenter effects

Less likely to occur as the researcher is not controlling the environment. These therefore can’t confound results, increasing the internal validity

Strength of Quasi Experiment: Less Experimenter bias

Experimenter doesn’t decide who is assigned to which condition so there’s less experimenter bias, improving the internal reliability

Strength of Quasi Experiment: Cause and effect can be established

If something is unethical or impractical to manipulate the IV ( too time consuming, expensive or not physically possible) this method can be used

Weaknesses of Lab experiments: Lacks/ low ecological validity

This is because the real world is not controlled. Results are less generalisable to explain the phenomenon in its real-world setting

Weaknesses of lab experiments: Experimenter effects

These are more likely to occur as the researcher is controlling the environment. These may confound results, reducing the internal validity

Weaknesses of Field Experiment: Low control

Uncontrolled so p’s are tested in an inconsistent/ changing environment so the results have low internal reliability

Weaknesses of Field Experiments: Extraneous Variables

These aren’t controlled so they could confound the results, reducing the internal validity, making cause and effect less clear

Weaknesses of Quasi Experiment: Low internal validity

Individual differences between conditions can confound the results, reducing the internal validity

Weaknesses of Quasi experiments: Similarity to lab & field

Quasi shares the same weaknesses as lab or field experiments, depending on where its conducted