Experimental Designs Flashcards
What are pilot studies?
Small-scale trial/study carried out before the full research to find out if there are any problems / make improvements.
What kind of problems do pilot studies check?
Experimental design = do ppl have enough time to complete the task?
Instructions to participants = are the instructions clear?
Measuring instruments = including behavioural categories in observation / questions in questionnaires. Allows them to be checked & modified where necessary.
What are the 3 types of experimental designs?
Repeated measures
Independent groups
Matched pairs
What is a repeated measures design?
Same participants take part in each conditions of the experiment.
Data obtained from both conditions is compared for each participant to see if there’s a difference.
What are the strengths of a repeated measures design?
= Fewer participants required =
since the same ppl do it twice - cheaper and less time-consuming since less ppl needed.
= Reduces participant variables =
there are no individual differences between 2 groups - EVs controlled - can establish cause & effect.
What are the weaknesses of a repeated measures design?
= Order effects =
same ppl doing both conditions - order effects - may perform better or worse depending on practice / fatigue effects - decreases internal validity.
= Demand characteristics caused =
bc ppl more likely to guess aim of study when they take part in both conditions.
What is practice and fatigue effects?
~Practice effects~
may perform better in 2nd condition as they know what’s expected of them.
~Fatigue effects~
may perform worse in 2nd condition because they give up.
How are order effects reduced?
Counterbalancing.
Sample split in half.
Half participants take part in condition A followed by B, and half do B followed by A.
Order effects are cancelled.
What is an independent groups design?
When 2 separate groups of ppl are in each condition of IV.
Random allocation is used - equal chance of being assigned to one group.
What are the strengths of an independent groups design?
= Reduces investigator effects =
since it also reduces a biased sample - decreases external validity.
= Avoids order effects =
participants take part in only 1 condition - less likely to be bored & give up.
= Reduces demand characteristics =
ppl do it once - less likely to guess aim of study - demand characteristics - high internal validity
What are the weaknesses of an independent groups design?
= More participants required =
as dif ppl take part in dif conditions - more expensive & time-consuming.
= Participant variables =
differences in age, sex, social background may affect results and act as an EV - difficult to establish cause & effect.
(Can be controlled using RANDOM ALLOCATION)
What is a matched pairs design?
Pairs of participants matched from target sample that have similar characteristics.
One member of each pair is placed in each condition - only do it once.
What are the strengths of using a matched pairs design?
= Reduces participant variables =
bc ppl are paired up so that each condition has people with similar abilities and characteristics.
= Less order effects =
ppl only take part once - less likely to get bored & give up.
What are the weaknesses of using a matched pairs design?
= More participants required =
dif ppl take part in dif conditions - more expensive & time-consuming - difficult to find close / exactly matched pairs (unless identical twins) - individual differences may still affect DV.
= Participant variables =
Cannot control for EVERY possible pps variable, so some may not be controlled - decreases internal validity.
How can a psychologist carried out a matched pairs design?
1~ Use a BASELINE assessment/questionnaire/interview/ask pps to self-report to collect data about their behaviours / characteristics.
2~ E.G. How much on average/daily recreational screen time (IV) do you use?
3~ Pps with SIMILAR recreational screen time use (or characteristics/IV) would be PAIRED.
4~ One pps from each pair would be (RANDOMLY) ALLOCATED in Group A and the other in Group B.
