Counterbalancing and Types of Experiments

This section delves into counterbalancing techniques and various types of experiments used in AQA Psychology Year 12 experimental designs.

Counterbalancing

Counterbalancing is an experimental technique used to overcome order effects in repeated measures designs.

Definition: Counterbalancing ensures that each condition is tested first or second in equal amounts across participants.

Two main approaches to counterbalancing:

1. AB or BA method: Divide participants into two groups, with each group experiencing conditions in opposite orders.
2. ABBA method: All participants take part in each condition twice, following the pattern ABBA.

Laboratory Experiments

Laboratory experiments are conducted in controlled environments.

Strengths:

• High internal validity due to control over extraneous variables.
• Precise operationalization of IV and DV.

Limitations:

• Participants' awareness of being studied may alter behavior.
• Artificial setting and materials reduce ecological validity.

Field Experiments

Field experiments are conducted in natural environments outside the laboratory.

Strengths:

• Higher ecological validity due to natural setting.
• Participants are often unaware of being studied, leading to more natural behavior.

Limitations:

• Difficulty in controlling extraneous variables.
• Ethical concerns regarding lack of informed consent and debriefing.

Natural Experiments

Natural experiments occur when the IV cannot be manipulated due to ethical or practical reasons.

Example: Studying the effects of a natural disaster on a population's mental health.

Strengths:

• High ecological validity due to real-world settings.
• Reduced demand characteristics as participants may be unaware of the study.

Weaknesses:

• Lack of control over the IV.
• Potential ethical issues related to studying sensitive situations.

Repeated Measures and Independent Group Designs

This section explores the characteristics, limitations, and mitigation strategies for repeated measures and independent group designs in AQA Psychology Year 12 experimental designs.

Repeated Measures Design

In a repeated measures design, all participants experience every level of the independent variable (IV).

Highlight: Repeated measures designs may suffer from order effects, including practice and boredom effects.

Limitations include:

• Practice effect: Participants may perform better on subsequent tests due to familiarity.
• Boredom effect: Performance may decline in later tests due to fatigue or disinterest.
• Participants may guess the experiment's purpose, potentially altering their behavior.

To address these limitations:

• Use equivalent but different tests to reduce practice effects.
• Implement counterbalancing to mitigate order effects.
• Present a cover story to prevent participants from guessing the study's aim.

Independent Group Design

In an independent group design, participants are divided into separate groups, each experiencing one level of the IV.

Highlight: Independent group designs cannot control for individual participant variables and require more participants than repeated measures designs.

Limitations include:

• Inability to control participant variables (e.g., individual abilities).
• Need for a larger sample size to obtain the same amount of data as repeated measures.

To address these limitations:

• Randomly allocate participants to conditions to distribute variables evenly.

Matched Pairs Design

This design uses two groups of participants, matching them on key characteristics that may affect the dependent variable (DV).

Definition: Matched pairs design involves pairing participants based on relevant characteristics and then randomly assigning one member of each pair to different experimental conditions.

Limitations include:

• Time-consuming process of matching participants.
• Difficulty in controlling all relevant participant variables.

To address these limitations:

• Restrict the number of variables to match on.
• Conduct a pilot study to identify key variables for matching.