experimental designs Flashcards
independent groups
participants are allocated to different groups where each group represents one experimental condition
experimental designs definition
the different ways in which the participants can be organised in relation to the experimental conditions
if there are two levels of IV, independent groups means
participants only experience one level of IV only
example of independent groups- energy drink example
one group would have energy drink (experimental condition) and the other group would drink water (control condition). performance would be compared and a difference in mean calculated
repeated measures definition
all participants take part in all conditions of the experiment
example of repeated measures -energy drink example
all participants would first experience experimental condition of drinking energy drink and would then later experience controlled condition of drinking water. the two mean scores would then be compared
matched pairs definition
pairs of participants are first matched on some variable that may affect the dependent variable. one member of the pair is assigned to condition A and the other to condition B
what does matched pairs aim to control
the confounding variable of participant variables
what does matched pairs often use
a pre-test to make matching effective
example of matched pairs- energy drink example
selected the two people that appear to be the chattiest and put one in condition A and the other in condition B, we would do the same with the 3rd an 4th participants and so on. the experiment is then run in the same way as independent groups
independent groups - limitation
-participant variables as the people in the two different groups are not the same.
-this means if the researcher finds a difference in the mean on the DV it may be to do with participant variables and not the IV
-this may act as a confounding variable so may reduce validity of findings –> to deal with this random allocation can be used
-less economical than repeated measures as twice as many people are needed so increases the amount of time an money recruiting participants
independent groups - strengths
-order effects are not a problem which they are for repeated measures
-participants are less likely to guess the aim
repeated measures - limitations
-participants have to do at least 2 tasks and the order of these can be significant. to deal with this, researchers often have to use counterbalancing
-order effects can arise as repeating two tasks can create boredom or fatigue which can decrease performance of the second task, however, participants may improve by second task. order acts as a confounding variable
-more demand characteristics as it is more likely that participants will work out the aim of the study. demand characteristics are more of a feature here than in independent groups
repeated measures - strengths
-participant variables controlled which means higher validity
-fewer participants needed so less time is spent recruiting them
matched pairs - strengths
-demand characteristics are less of a problem as participants are only taking part in a single condition
