Reliability is the consistency of your measurement, or the degree to which an instrument measures the same way each time it is used under the same condition with the same participants. In short, it is the repeatability of your measurement.
A measure is considered reliable if a person's score on the same test given twice is similar. It is important to remember that reliability is not measured, it is estimated.
There are two ways that reliability is usually assessed: test/retest and internal consistency.
Test/Retest
The idea behind test/retest is that you should get the same score on test 1 as you do on
test 2.
Internal Consistency
Internal consistency estimates reliability by grouping questions in a questionnaire that measure the same concept.
For example, if a respondent expressed agreement with the statements "I like to ride bicycles" and "I've enjoyed riding bicycles in the past", and disagreement with the statement "I hate bicycles", this would be indicative of good internal consistency of the test.
The primary difference between test/retest and internal consistency estimates of reliability is that test/retest involves two administrations of the measurement instrument, whereas the internal consistency method involves only one administration of that instrument.
Term used in psychology to question whether something measures that which it purports to measure. Given the great debate about intelligence any IQ test can be questioned on the grounds of its validity. Psychology immediately asks the question 'Does this test measure this thing we call intelligence?' Is it valid?
External validity refers to our ability to generalise the results of our study to real life settings.
Internal Validity asks if there is a relationship between the program and the outcome we saw, is it a causal relationship? For example, does the IV affect the DV?
Ecological validity: The degree to which an investigation represents real-life experiences.
Back to Homepage