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psy 321 > exam 1 > Flashcards

exam 1 Flashcards

1
Q

3 features of an experiment

A
  1. vary at least one or more independent variable (s)
  2. assign participants to experimental conditions in a way that ensures their equivalence
  3. experimental control
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2
Q

how do we know if an iv is strong enough to test/ has been manipulated enough?

A

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

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3
Q

how do groups get roughly equivalent groups for each condition?

A

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)

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4
Q

what are the two types of experimental design?

A

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)

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5
Q

characteristics of a within subject design

A
  • 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)
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6
Q

how to minimize order effects

A

counter balancing: diff participants complete levels of IV in diff orders
- latin sqaure design: method of counterbalancing where all possible orders are used

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7
Q

within vs between subjects design when…

A

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

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8
Q

what is experimental contol ?

A

experimental contol: hold extraneous varibles constant

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9
Q

systematic variance vs error variance vs confound

A

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

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10
Q

internal validity

A

degree to which a researcher can draw accurate conclusions about the effects of an IV
- relies on elimination of confounds
-achieved through experimental control

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11
Q

what is biased assignment?

A

threat to experimental control

people are put into groups in biased / non random way (between subjects)

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12
Q

what is differential attrition?

A

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

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13
Q

what is pretest sensitization?

A

threat to experimental control

when taking pretest changes you
- participant reats differently to IV than they would have if not presented with pretest (within)

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14
Q

what is ‘history’?

A

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

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15
Q

what is maturation?

A

threat to experimental control

peoples natural development (within)
- internal changes in the participant during the experiment

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16
Q

what is regression to the mean?

A

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

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17
Q

what is instrumentation?

A

threat to experimental control

changes in the measurement tool across conditions or testings (within & btwn)
- make sure instruments are calibrate

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18
Q

what is diffusion?

A

threat to experimental control

participants in diff conditions communicate w/ each other (btwn)
- ruins ability to detect IV

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19
Q

what is lack of standardization?

A

threat to experimental control

there is no standardized procedure: scripts, trained experimenters, same: time, temp, location, lighting, noise level

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20
Q

what is design confounds?

A

threat to experimental control

order effects could be confounds (within)

21
Q

what is experimenter expectancy effects?

A

threat to experimental control driven by people involved

the researchers expectations about the outcome of a study influences participants reactions
- keep experiment blind

22
Q

what is demand characteristics?

A

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

23
Q

what is social desirability / evaluation appehension?

A

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”

24
Q

what is the placebo effect?

A

threat to experimental control driven by people involved

when someone experiences a change because they expect a change

25
Q

what is the Hawthorne effect?

A

threat to experimental control driven by people involved

actualy knowing that you are in an experiment leads to diff outcomes than would normally occur
-have both groups think they’re in the study or not

26
Q

what is error noise?

A

static in the measurement
- messes up both groups
- “waters down the experiment” =n effect is not as strong
- related to reliability

27
Q

what is external validity?

A

degree to which results obtained in one study can be replicated or generalized

28
Q

what is “across situations” in external validity ?

A

can results of study be generalized in a different study ?
- ecological validity: generalized to real world
- mundane realism: experiment is similar to real life situations in a lab setting
- psychological realism: psychological processes are similar to those in real life situations (does it FEEL real?)

29
Q

what is “across people” in external validity ?

A

do people in sample generalize to a more broad population?
- random selection of participants is best
-most common psych participants fall into: Western Educated Industrialized Rich Democratic

30
Q

what is “across operationalization” in external validity?

A

same outcome if we had measured our conceptual variable differently

31
Q

t statistic

A

estimated standard error of population based on sample
- the denominator is always diff bc sample variance changes from sample to sample unlike pop variance that is same for all

32
Q

why is variance used instead of standard deviation

A

standard deviation is descriptive and biased vs variance which is inferential and unbiased

33
Q

degrees of freedom

A

n-1
- the bigger the df, the better the sample, bigger sample better reflects the population

34
Q

t disributions

A
  • smaller distributions (smaller sample sizes) have more variability / flatten out
  • as sample size gets bigger, distribution is closer to normal distribution
  • shape of t distribution changes with df
35
Q

what does numerator in one sample t test represent?

A

actual difference between pop and sample mean

36
Q

what does denominator in one sample t test represent?

A

average (expected) of how sample differs from pop mean

37
Q

assumptions of t test

A

-independent observations
- population sampled must be normal

38
Q

advantages of a t test

A

population mean and pop standard error are not needed

39
Q

independent measures / btwn subjects is..

A

design involves 2 seperate and independent samples and makes a comparison btwn 2 groups

40
Q

repeated measures / within subjects is…

A

two sets of data obtained from same sample

41
Q

what does the numerator in a t test for independent samples mean?

A

sample mean diff - pop mean diff

42
Q

what does the denominator in a t test for independent samples mean?

A

standard error of sample mean difference

43
Q

standard error

A

amount of error expected when you use sample mean diff to estimate pop mean difference (how well sample represents pop)

44
Q

assumptions of independent t tests

A
  • observations are independent
  • 2 population samples are selected from are normally distributed
  • homogeneity of variance: two populations the samples are selected from must have same variance (fmax should not be sig for there to be homogeneity of variance)
45
Q

the two types of related measures t test are:

A

repeated measures: single sample of individuals is measured more than once on the same dependent variable

matched subject study: each individual in one sample is matched on a specific variable with a subject in another sample

there is less variance/ less standard error/ bigger t bc we’re comparing ppl to themselves

46
Q

big diff betwn related t test and others

A

comparison distribution is no longer just a sample mean; comparison distribution is now mean difference score

47
Q

what is difference scores?

A

value obtained from subtracting the before treatment score from after treatment score (x2-x1)

48
Q

assumptions of related measures t test

A

-observations must be independent
- population distribution of d scores must be normal

psy 321 (3 decks)

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