Lesson 5 (experimental designs) Flashcards
Experimental group
the group of participants that are exposed to the IV
3 Experimental designs
independant measures
repeated measures
matches pairs
Repeated measures
All participants recieve all levels of the IV. The DV is then compared in each condition.
eg. each participant does a memory test after drinking caffiene, they do a similar test a week later without caffiene.
Advantages of repeated measures
Controls participant variables: Participants are kept the same as they take part in all conditions
Fewer participants, more economical
Weakness of repeated measures
Order effects: A participant gave the same test on a different occasion may do better due to practice (practice effects)
Demand characteristics: as participants are taking part in all conditions, they may guess the aim and change their behaviour
Ways of dealing with weakness, repeated measures
Practice effects: use two different equivelant tests
order effects: use counterbalancing, do A, B, B, A
Demand characteristics, deception (participants are not aware of the research aims) or a single blind design (they do not know which condition of the experiment they are recieving)
Independent measures design
Participants are placed in seperate (independant groups). Each group only does one level of the IV.
eg. to test the effect of caffeine on memory, one group of parrticipants are given coffee, another group are not (IV) both groups have a list of words to recall
Advantages of independant measures
No order effects, participants only do one condition, performance less likely to improve due to practice or get worse due to boredom (boredom effect)
Demand characteristics: Less likely to occur, less likely to guess tue aims as theyre only taking part in one condition.
Weakness of independant measures
Participant variable differ between groups which can be confounding unless controlled
More participants needed, less economical
Ways of dealing with weakness, independant measures
Participant variables: participants randomly allocated into each group to evenly distrubute participant variables.
Can be done by putting a name into a hat
Matched pairs design
Similar to independant measures, but participants are matched on key characteristics (age, gender, intelligence) that may effect the outcome (DV)
Each member of the pair is then randomly allocated group A or B.
Advantaged of matched pairs
Participant variables: kept more constant between both conditions
No order effects: participants only participate in one condition
Demand characteristics: less of a problem, only one condition
Disadvantages of matched pairs
Participant variables: can never be perfectly matched in all aspects
Matching participants is time consiming and difficult
More participants required, less economical
Ways of dealing with weaknesses, matched pairs
Restruct number of variables to matched to make it easier
Conduct a pilot study to consider key variables that might be important when matching
