experimental design

independent groups

Different participants are used in each condition of the experiment.

strengths of I

• No order effects (practice or fatigue)

• Simple to set up

• lowers risk of demand characteristic as harder to work out if they only experience one level of IV

limitations of I

• Participant variables may differ between groups → can confound results

• Requires more participants= time and money

repeated measure

The same participants take part in all conditions of the experiment.

what technique is used to minimise participant variable

Random allocation

Definition:
A technique used in independent groups designs to assign participants to conditions randomly, ensuring each participant has an equal chance of being in any condition.

Purpose / Strength:

• Controls participant variables → reduces confounding

Key terms for AQA: independent groups, participant variables, random.

strength of repeated

• Controls participant variables (same people in all conditions)

• Fewer participants needed

limitation of repeated

• Order effects (practice, fatigue, boredom)

• Demand characteristics more likely

how are order effects reduced

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

Example:

• Half of participants do Condition A first, then Condition B.

• The other half do Condition B first, then Condition A.

matched pairs

Different participants are used in each condition, but they are matched on key characteristics (e.g., age, IQ) to make groups as similar as possible.

strengths of matched

• Reduces participant variables compared to independent groups

• No order effects

limitations of matched

• Time-consuming to match participants accurately

• Matching can never be perfectly remove participant variable

what reduces reascher bias

Randomisation

Using chance to decide the order of trials, presentation of materials, or selection of participants

Reduces researcher bias, ensures fairness

how can we increase reliability and control EVS

Standardisation

Keeping procedures, instructions, and conditions the same for all participants

Controls extraneous variables, ensures reliability