exam 1 Flashcards
(48 cards)
3 features of an experiment
- vary at least one or more independent variable (s)
- assign participants to experimental conditions in a way that ensures their equivalence
- experimental control
how do we know if an iv is strong enough to test/ has been manipulated enough?
pilot test: little version of actual experiment to get a sense of how things are going ; great for finding mistakes
manipulation check: question that you ask participants to see if independent variable had an effect
how do groups get roughly equivalent groups for each condition?
self selection: participants choose condition themselves (bad bc diff types of ppl in conditions)
arbitrary assignment: assignment based on a rule (could still put diff types of ppl in conditions)
matching on multiple variables: each participant has a ‘twin’ in other condition (hard to do)
random assignment: putting them in group based on random number (best way to ensure equivalence)
what are the two types of experimental design?
between subjects design: each participant is tested under only one condition/level
within subjects design: each participant is tested under every condition / level of IV (repeated measures)
characteristics of a within subject design
- looks like pretest / post test design
- pros: more powerful (ability to detect differenes / effects in group) , fewer ppl needed
- cons: order effects (practice, fatigue), sensitization (figuring out what study is about), carryover (effect in 1 condition lingers onto next)
how to minimize order effects
counter balancing: diff participants complete levels of IV in diff orders
- latin sqaure design: method of counterbalancing where all possible orders are used
within vs between subjects design when…
within : order effects are not a problem, powerful design is wanted, there are scarce participants, you want to generalize, participants are exposed to multiple levels of treatment
between: order effects are a problem, there is large # of participants, in real life people receive one not both levels / conditions
what is experimental contol ?
experimental contol: hold extraneous varibles constant
systematic variance vs error variance vs confound
systematic variance: variance across experimental groups (differences between groups)
error variance: is everything we’re not looking for (variance between groups)
confound: variable other than IV differes between groups (systematic)
- treatmment + confound = systematic
internal validity
degree to which a researcher can draw accurate conclusions about the effects of an IV
- relies on elimination of confounds
-achieved through experimental control
what is biased assignment?
threat to experimental control
people are put into groups in biased / non random way (between subjects)
what is differential attrition?
threat to experimental control
‘mortality’ / people dropping out of a study (within & between subjects)
only a confound if one group has drop outs and other does not
what is pretest sensitization?
threat to experimental control
when taking pretest changes you
- participant reats differently to IV than they would have if not presented with pretest (within)
what is ‘history’?
threat to experimental control
anything happening outside of study that might account for the outcome (within & between)
-local history effect: something outside is influencing one group but not the other
- how to reduce: shorter time inverals btwn pre and post test & replicate studies
what is maturation?
threat to experimental control
peoples natural development (within)
- internal changes in the participant during the experiment
what is regression to the mean?
threat to experimental control
if one sample of is extreme, the next sampling is likely to be closer to its mean (within)
- dont test extreme groups if possible
-have control group thats equally extreme
what is instrumentation?
threat to experimental control
changes in the measurement tool across conditions or testings (within & btwn)
- make sure instruments are calibrate
what is diffusion?
threat to experimental control
participants in diff conditions communicate w/ each other (btwn)
- ruins ability to detect IV
what is lack of standardization?
threat to experimental control
there is no standardized procedure: scripts, trained experimenters, same: time, temp, location, lighting, noise level
what is design confounds?
threat to experimental control
order effects could be confounds (within)
what is experimenter expectancy effects?
threat to experimental control driven by people involved
the researchers expectations about the outcome of a study influences participants reactions
- keep experiment blind
what is demand characteristics?
threat to experimental control driven by people involved
participants catch onto point of study and change their behavior to how they think they should behave
what is social desirability / evaluation appehension?
threat to experimental control driven by people involved
just want to look good, not giving honest responses to portray in a positive light
- make anonymous
-“be honest”
what is the placebo effect?
threat to experimental control driven by people involved
when someone experiences a change because they expect a change
