2.3.3 Experimental designs Flashcards
what is the experimental group?
the group getting the experimental treatment - IV manipulated
what is the control group?
the group receiving non experimental treatment e.g. placebo group
what do the placebo group provide?
baseline for comparison
what does the term experimental design refer to?
how psychologists allocate their participants to groups
when do you have an experimental design?
when carrying out experiments - lab, field, quasi
what is an independent measures design?
participant takes part in one condition of the experiment (either experimental or control)
in an independent measures design how are participants allocated to groups?
randomly allocated
what are the 2 strengths of independent measures designs?
reduces risk of demand characteristics
reduces order effects
(strength) independent measures reduces risks of demand characteristics. What are demand characteristics?
where participants try to figure out the aim of the study and change their behaviour accordingly (Hawthorne effect, Screw you effect)
how does an independent measures design reduce the risk of demand characteristics?
less opportunity for participants to work out the aim of the study - they only do it once, this increases validity
(strength) independent measure reduces order effects. What are order effects, what are the 2 types?
effects from previously having completed the research
practice effects - participant does better as they’ve already done it
fatigue effects - participant do worse due to being bored or tired
how does an independent measures design reduce the chance of order effects?
person only does the research once
what are two weaknesses of independent measures designs?
individual differences - accidental bias
expensive and time consuming
(weakness of independent measures) what does it mean that results may be affected by individual differences? what could it influence?
groups may not be identical
differences could influence validity of results
(weakness) why can independent measures designs be expensive and time consuming?
need to find more participants
e.g. want to test 100 people, you need 200 as 100 will be needed for the control group
what does a repeated measures design involve?
participants participate in both conditions
what are strengths of repeated measures designs?
quick and cheap
not affected by individual differences
(strength) why are repeated measures quick and cheap?
you don’t have to find more participants - the same ones participate in both conditions
(strength) why are repeated measures not affected by individual differences?
the same people participant in each condition - no differences between groups, no effect on validity
what are two weaknesses of repeated measures designs?
demand characteristics
order effects
(weakness) why do repeated measures have the risk of demand characteristics?
participants participate twice - can try to figure out the aim of the study and change their behaviour accordingly
(weakness) why do repeated measures have the risk of order effects?
participants are repeating the same task (practice/fatigue)
what technique can be used to overcome order effects?
counterbalancing
what does counterbalancing involve?
half the participants do the experimental condition followed by the control
half the participants do the control condition followed by the experimental
what does a matched pairs design involve?
participants only participate in one condition but are matched according to characteristics and one is placed in the experimental condition and the other the control
who are the best matched pairs carried out on and why?
identical twins
because they grow up in similar environments with similar characteristics
what are two strengths of matched pairs designs?
reduce order effects
not affected by individual differences
(strength) how do matched pairs reduce order effects?
each participant participates in each condition once so they wont show fatigue or practice effects
(strength) why are matched pairs not affected by individual differences?
participants are matched according to characteristics - groups are as identical as possible
what is a weakness of matched pairs?
expensive and time consuming
why are matched pairs expensive or time consuming?
you have to match participants
or
take the time looking for identical twins willing to participate
