Experimental research Flashcards
what is an experiment?
when one or more variables are manipulated to test a cause-effect relationship
what is an experimental/alternative hypothesis?
treatment leads to an effect
what is a null hypothesis?
treatment does not lead to an effect
what is a nuisance variable?
an additional factor that affects the dependent variable
how can nuisance variables be dealt with?
they can be turned into control variables
how can nuisance variables become confounding variables?
if they change across conditions
if the nuisance variable varies across all levels of the independent variable…
hold the variable constant for all participants
if nuisance variable varies across participants…
randomly assign participants to treatment across
counterbalancing
vice versa for the other half of participants
what is an experiment group?
they receive the important level of the independent variable
what is a control?
they serve as the untreated comparison group
if you have more than one IV, what should you do?
include them in the same experiment
why is it better to test IVs in the same experiment?
- more efficient
- better control of nuisance variables
- results will be more representative of real behaviour
benefits of measuring more than one DV
it is usually more informative
limitations of measuring more than one DV
these variables might not measure the same thing, e.g., the speed-accuracy trade off
advantages of experimental research
- relative strong test of causality
- can manipulate a variety of controls, making it easier to eliminate nuisance variables
disadvantages of experimental research
- unnatural settings and tasks reduce ecological validity
- some phenomena cannot be studied under controlled conditions, e.g., social interaction
- ethical limitations
within-subjects design
repeated measures design
where all participants receive all levels of the IV
advantages of within-subjects design
- fewer participants needed
- reduced individual differences
disadvantages of within-subjects design
- carryover effects
- effect of one carries over between conditions
how can disadvantages of within-subject design be dealt with
- randomly allocating participants to groups
- using matched participants design
between-subjects design
independent measures design
where different groups of participants receive different levels of the IV
advantages of between-subjects design
- no order effects
- some experiments can only be between-subjects, e.g, health or clinical interventions, or learning a skill
- naive participants
disadvantages of between-subjects design
- lots of participants
- more expensive
- individual differences
how can disadvantages of between-subject design be dealt with
randomising or counterbalancing the order of conditions
what is counterbalancing?
a way to negate carryover effects
problem with counterbalancing
it is too complicated to carry out when there are a high number of conditions
what is the latin square design?
where each condition occurs equally at each stage of the experiment, e.g., ABCD each appear in all orders
problem with latin square design
carryover effects are still possible
what are quasi-experiments?
one (or more) IVs are selected, but not manipulated
advantages of quasi-experiments
ability to examine variables that would be unethical to manipulate
disadvantages of quasi-experiments
- participants are not randomly assigned to IV levels, which can lead to confounding variables
- impossible to make strong conclusions about cause-and-effect
random sample
everyone has an equal chance of being chosen
limitations of random sample
practically difficult to carry out, and often likely to be opportunity sampling
stratified sample
random selection of each subgroup of the population
quota sample
representative sample that meets quotas and targets
what is EEG?
measures brain activity by placing electrodes on the scalp
advantages of EEG
- excellent temporal resolution
- relatively inexpensive
disadvantages of EEG
- poor spatial resolution
- artifacts (something else can cause an effect)
- only surface activity information
what is fMRI?
gives 2d and 3d views of the brain and measures activity through blood oxygen
advantages of fMRI
- excellent spatial resolution
- access to all areas of the brain
disadvantages of fMRI
- poor temporal resolution
- movement is restricted
- expensive
- claustraphobic
