Experimental Methods Flashcards
what is an experiment?
manipulation of one or more variables
determine the effect of the manipulation
test cause effect between variables
what are the two types of hypotheses
- alternative / experimental
- null
what is alternative hypothesis?
treatment leads to effect
what is a null hypothesis
treatment does not lead to effect
what is the relationship between a dependant variable and independent variable?
manipulating the independent variable changes the value of the dependant variable
what is a nuisance variable?
additional factor that affects the dependant variable
how do you deal with a nuisance variable?
turn it into a control variable
randomly assign ppt to groups
counterbalancing
include a control group
what is an experimental group?
group receiving the important level of the independent variable
what is a control group?
untreated comparison group
what to do if you have more than one independent variable?
change a nuisance variable into an IV
and include in one experiment
advantages of experiments
relative strong test of causality
possibility of a variant of manipulative controls
disadvantages of experiments
unnatural settings & tasks
reactivity
some phenomena cannot be studied under controlled conditions
ethical limitations
what does within subjects design mean
repeated measures - all ppt recieve all levels of independent variable
what does between subjects design mean?
independent groups - different groups receive different levels of the IV
what to do if nuisance variable varies across all levels of the independant variable?
hold the variable constant for all ppt
what to do if the nuisance variable varies across the ppt?
randomly assign ppt to conditions
give 2 other ways to deal with nuisance variables?
- counterbalancing
- include a control group
why is testing more than one IV in one experiment better than several experiments (3)
- more efficient
- better control of nuisance variables
- results often more representative of behaviour
whats the difference between nuisance and confounding variables?
nusiance variables BECOME confounding variables when their effects differ between the conditions
3 advantages of between subject design
- no order effects
- some experiments can only be between
- naive participants
2 disadvantages of between subject design?
- lots of ppt needed
- individual differences
how to counteract disadvanatges (2)
on between subject
- random assignment
- match ppt on characteristics
2 advantages of within subject design?
- fewer ppt needed
- reduced individual differences
disadvantages of within subject design
- carryover effects - effect over one carries on to next session
how to counteract within subject design disadvantages?
counterbalancing
random order
latin square design
what is a quasi experiment?
one or more independant variable selected but not manipulated
advantage of quasi experiments?
can examine variables that would be unethical to manipulate
disadvantage of quasi experiments
no strong conclusion about cause and effect
how to improve quasi experiments? (2)
- match ppt
- if treatment study - test before and after
what are the 3 sampling types?
- random
- stratified
- quota
what is random sampling?
everybody has a equal chance of being selected
what is stratified sampling?
random selection of each subgroup of the population
what is quota sampling?
representative sample that meets targets
what are psycho physiological measurements?
testing the effect of psychological variables on physiological processes
whats one example of psycho physiological measurements?
brain imaging
what does brain imaging do?
look at localisation and timing of brain functions
what are three ways to measure the brain?
- EEG
- ERP
- FMRI
what is a EEG (electroencephalography)
electrodes placed on scalp
detect and measure patterns of electrical activity
advantages of EEG (2)
- excellent temporal resolution
- relatively inexpensive
disadvantages of EEG (3)
- poor spatial resolution
- artifacts from eye movements ect
- surface activity only
what is a fmri
(functional magnetic resonance imaging)
2D and 3D view of the brain
measures the amount of blood oxygen
advantages of fmri (2)
- excellent spatial resolution
- accesses all areas of the brain
disadvantages of fmri (4)
- poor temporal resolution
- expensive
- claustrophobia inside scanner
- ppt must not move
