the extent to which a measurement is consistent and free from erro
validity
assures that a test is measuring what it is intendedto measure
measurement error
"noise" that gets in the way of our finding the true score
systematic errors
predictable errors of measurement
random errors
errors due to chance and can affect a subject's score in an unpredictable way from trial to trial
regression towards the mean
a statistical phenomenon in which scores on a pretest are likely to move toward the group mean on a posttest becasue of inherent positive or negative measurment error; also called statistical regression
reflects the degree of association between two sets of data, or the consistency of position within the two distributions
test-retest reliability
used to establish that an instrument is capable of measuring a variable with consistency
testing effect
when the test itself is responsible for observed changes in a measured variable
interrater reliability
variation between two or more raters who measure the same group of subjects
intrarater reliability
the stability of data recorded by one individual across two or more trials
alternate forms reliability
testing that is used as an alternative to test-retest reilability with paper-and-pencil tests, when the nature of the test is such that subjects are likely to recall their responses to test items
internal consistency
(homogeneity); reflects the extent to which items measure various aspects of the same characteristic and nothing else
split-half reliability
a reliability measure of internal consistency based on dividing the items on an instrument into two halves and correlating the results
facet
in generalizability theory, specific conditions under which reliability of a measurement can be generalized
minimal detectable difference (MDD)
the amount of change in a variable that must be achieved to reflect a true difference; the smallest amount of change that passes the threshold of error. Also called minimal detectable change (MDC)