ch 3: Defining and measuring variables Flashcards
variable
characteristic or condition that changes or has different values for different individuals
constructs or hypothetical constructs
hypothetical attributes or mechanisms that help explain and predict behaviour in a theory (eg. motivation)
theory
set of statements about the mechanisms underlying a particular behaviour; generates predictions
operational definition
procedure for indirectly measuring and defining a variable that cannot be observed or measured directly; specifies a measurement procedure (a set of operations) for measuring an external, observable behaviour and uses the resulting measurements as a definition and a measurement of the hypothetical construct; measures and defines construct
operationalizing a construct
process of creating an operation definition for a construct (clustering behaviours associated with concept as a measurement of it and defining it)
example of a construct; operational def
intelligence; IQ test
limitations of operational definitions (
(1) not a one-to-one relationship between the variable that is being measured and the actual measurements produced by operation defs, (2) can leave out important components of a construct (tip: include multiple procedures for measuring same variable) and (3) may contain extra components that are not part of the construct being measured
criteria for evaluation the quality of any measurement procedure (2)
(1) validity and (2) reliability
validity
whether a measurement procedure is actually measuring what it claims to be measuring
types of validity (6)
(1) face, (2) concurrent, (3) predictive, (4) construct, (5) convergent, and (6) divergent
face validity
least scientific; based on superficial appearance or face value of a measurement procedure
concurrent validity
comparing to established procedure
predictive validity
accurately predict behaviour
construct validity
a variable behaves in exactly the same way as the variable itself (comparing to past research)
convergent validity
different methods for measuring the same construct have related scored
divergent validity
measuring two different constructs and having scores NOT relate
reliability
stability or consistency of a measurement
measured score = _____ + _____
true score; error
sources of error (3)
(1) observer, (2) environmental, and (3) participant
types of reliability (4)
(1) test-retest, (2) parallel-forms, (3) inter-rater, and (4) split-half
split-half reliability
slitting the items on a questionnaire or test in half, computing a separate score for each half and then calculating the degree of consistency between the two scores for a group of participants
accuracy
degree to with the measurement conforms to the established standard
scale of measurment
set of categories that measurements are classifying individuals into
types of measurement scales (4)
(1) nominal, (2) ordinal, (3) ratio, and (4) interval
nominal scale
quality not quantity (eg. hair color)
ordinal scale
ordered series without equal intervals; rank; can tell direction of difference but not magnitude (eg. t-shirt size)
interval scale
sequential with each interval being the same, no absolute zero (eg. celcius)
ratio scale
sequential with each interval being the same, WITH absolute zero (eg. weight)
modalities of measurement (3)
(1) self-report, (2) physiological and (3) behavioural
advantage of self-report
most direct way to assess a construct
advantage of physiological measures
objective
disadvantage of physiological measures
is it measuring the construct? expensive!
ceiling effect
when the range is restricted at the high end
floor effect
clustering at the low end of the scale; restricted range
range effect
ceiling and floor effects
artifact
nonnatural feature accidentally introduced into something being observed (ie. external factor); can threaten validity and maybe reliability
common artifacts (2)
(1) experimenter bias and (2) participant reactivity
reactivity
participants modifying behaviour in response to being a participant in a study or knowledge that they are being measured
subject role (behaviours) (4)
(1) good subject role, (2) negativistic subject role, (3) apprehensive subject role, and (4) faithful subject
