unit 11: Evaluating Measurements and Data Quality Flashcards
measurement
involves rules for assigning numeric values to qualities of objects ti designate the quantity of the attribute
>attributes are not constant
>
advantages of measurement
it removes the guess work when gathering information
obtain reasonably precise information
measurement is a language of communication
less vague
errors of measurement
obtained score = true score+/- error
true score is
the true value that would be obtained if it were possible to have an infallible measure of target attribute
the error of measurment
the difference between true and obtained scores-reflects extraneous factors that affect the measurement and distort the results
main factors contribute to error measurement
>situation contaminants >response set biases > transitory personal factors >administration variation >item sampling
reliability
is the consistency with which an instrument measures the attribute
stability
important factor for stability measures the extent to which the same scores are obtained when the instrument is used with the same people on separate occasions
test-retest reliabilty
assessment of stability researchers administer the same measure to a sample of people on two occasions and then compares the scores
reliability coefficient
a numeric index of a measure’s reliability, to objectively determine exactly how small the difference are. (r) range from 0.00-1.00 the higher the # the more reliable
internal consistency
scales that involve summing items usually are evaluated for their internal consistency
>reliability to the extent that all its sub parts measure the same characteristic
cronback data/coefficient alpha
this method gives an estimate of split-half correlation for all possible ways of dividing the measure into halves, not just odd versus even items
equivalnce
approach to estimating reliability-used primarily with observational instruments-determines the consistency or equivalence of the instrument by different observers or rater
interrater/interobserver reilability
degree of error can be assessed, which estimated by having two or more trained observers make simultaneous, independent observation
interpretation of reliability coefficient
are an important indicator of an instrument’s quality,
> reliability estimates vary according to the procedure used to obtain them
>instrument is related to sample heterogeneity
validity
is the degree to which an instrument measures what is supposed to be measuring.
> reliability and validity of an instrument are not totally independent
face vailidity
refers to whether the instrument looks as though it is measuring the appropriate construct