experimental design Flashcards
what is experimental design
how people are organised into experimental groups of an investigation
what is this often confused with
experimental method - lab, field, natural and quasi experiments
what is an independent groups design
where the researcher recruits a group of participants
then they divide them into 2
one group does condition one, then the other group does condition 2
compare the results
strengths of independent design
order effects are reduced as participants only take part in one condition- they don’t get to practice the task or become fatigued
demand charateristics are reduced as participants only take part in one condition they are less likely to guess the aim of the study
weaknesses of independent groups design
there are participants extraneous variable between the groups lowering the internal validity of the study (eg may accidentally get a lot of intelligent people in one condition)
how are participants randomly allocated
the lottery method - draw the names out of a hat to ensure that there is no bias
random number generator
what is a repeated measures design
where all participants take part in both conditions of the experiment ( they repeat the experiment)
they all complete condition 1 and then they would all complete condition 2
what are the strengths of repeated measures
participant extraneous variable are controlled for (reduced, never eliminated)
less participants needed as they are in both conditions
what are the weaknesses of repeated measures design
order effects - this is an extraneous variable where the order in check conditions of the experiment effects the results eg. practice effects or fatigue effects
demand characteristics- a cue that makes participants unconsciously aware of the aims of a study or helps participants work out what the researcher wants to find and this causes them to change their behaviour
what is a matched pairs design
different participants complete in each of the two (or more) conditions of the experiment. participants are first assessed ranked on a characteristic (eg aggression
how do you conduct a matched pairs design
recruit a group of participants
they match the participants on specific variables such as age or IQ
what are the strengths of matched pairs design
participants only take part in a single condition, so order effects and de,and characteristics are less of a problem.
participant extraneous variables are reduced (never eliminated)
weaknesses of matched pairs design
although there is a decrease in participant variables the participants cannot truly matched time consuming and expensive, so less economical then the other designs.
what is counterbalancing
reduces the order effects although they can never be fully eliminated
a method to reduce the impact of order effects
