EXPERIMENTS Flashcards
Experimental method
Manipulate situations, deliberately set up situations, watch and record what happens.
Experiments have an IV and a DV.
Independent variable
Made to change by experimenter
Dependent variable
Observed/ measured by experimenter
Cause and effect relationship
Relationship between two events/ situations, one of the two is cause of the other.
Control other variables as well as measuring IV and DV allows us to test cause and effect.
comparison condition
To find out if IV affected DV, this condition is where there is a different level of the IV.
3 Experimental designs
Independent measures
Repeated measures
Matched pairs
Independent measures design
Using different ps in each condition.
E.g giving one group of ps one test and a different group the same but in a different condition.
Giving one group a driving test after alcohol, and another group the same test sober.
Strengths of IMD
-NO ORDER EFFECTS- practice; 2nd time may be better
fatigue; 2nd time ps may be worse, bored.
-REDUCE EXPOSURE TO DEMAND CHARACTERISTICS- ps only see condition one time, less likely to change their behaviour.
Weaknesses of IMD
-INDIVIDUAL DIFFERENCES- intelligence levels can differ and distort results between conditions.
-MORE PS NEEDED- 2 groups of different people may be less ethical and harder to find, also time consuming.
Repeated measures
Using same ps in each condition of experiment
Strengths of RMD
-ELIMINATES INDIVIDUAL DIFFERENCES- participant variables like intelligence.
-FEWER PS USED- good when ps are hard to find.
Weaknesses of RMD
-ORDER EFFECTS- fatigue & practice can distort results
-EXTRANEOUS VARIABLES
-INCREASED EXPOSURE TO DEMAND CHARACTERISTICS- ps see experimental task more than one time.
Matched pairs design
Using similar, but different, ps in each condition, such as twins, match ps on any important characteristics that may affect performance.
Strengths of Matched
-CONTROLS FOR INDIVIDUAL DIFFERENCES- they will have been carefully matched
-ORDER EFFECTS & DEMAND CHARACTERISTICS LESS OF AN ISSUE- each ps only takes part in one condition, unlike repeated measures.
Weaknesses of Matched
-INDIVIDUAL DIFFERENCES CAN NEVER BE PERFECTLY MATCHED
-DIFFICULT to match subjects
-TIME CONSUMING to find match, may not even be possible.
Counterbalancing
Overcomes problems of order effects.
Used for Repeated measures design.
-Alternating the order of ps doing conditions to average out order effects.
- AB – BA
(Half ps do condition A then B , other half do condition B then A)
Single blind procedure
Overcomes problems of demand characteristics.
-Ps unaware of aims and/or which condition they’re in.
Double blind procedure
Protects against both demand characteristics and experimenter bias.
-Ensures neither the researcher nor ps are aware of condition individual is in.
Extraneous variables
Can affect the DV (what is measured) and need to be controlled for.
-These are other factors apart from the IV that can affect outcome of an experiment (the DV).
2 main types of extraneous variables:
Situational variables
Participant variables
Situational variables
Outside influences on experiment, such as time of day, weather, noise, room experiment is in etc…
Order effects such as practice/fatigue occur when ps is asked to undertake task more than once (RMD)
How to control situational variables
1) STANDARDISATION; all instructions given, procedures followed, scoring techniques and environment must be identical for all ps tested.
2) COUNTERBALANCING; changes to the order of tasks for each ps, or use of ABBA technique. (controls for order effects)
3) RANDOMISATION; order of tasks, presentation of data is decided randomly to control for order effects.