measures.pptxMeasures
Week 6
Reliability
A measurement instrument is reliable if responses to it are consistent.
Appraising internal consistency reliability:
A correlation of .90 or more is considered excellent internal consistency.
Good internal consistency ranges from .80 to .89.
Lower than that (down to .60) can be acceptable for monitoring client progress, but is not appropriate for diagnostic purposes.
Validity
The fact that an instrument is consistent doesn’t mean that it measures what it is designed to measure.
The degree to which an instrument captures the phenomenon that it is designed to measure is its validity.
To be useful, instruments should be both reliable and valid.
Face validity refers to whether or not an instrument appears to measure what it is intended to measure.
Content validity is established if it appears to fully capture the range of indicators of the phenomenon of interest.
Criterion validity is established by testing the instrument on a group of people to see if it correlates with some external, independent indicator of the same phenomena.
In order to have construct validity, an instrument should correlate more strongly to the concept it was designed to measure as opposed to other concepts .
Locating instruments
There are three main sources for locating assessment instruments:
Publishing houses that sell copies of instruments.
Reference books that review and appraise different assessment instruments for different target problems.
Searching the literature, including research and web sites.
Selecting instruments
Has there been a study testing the instrument to show it is valid and reliable?
Has a study been conducted with your specific population?
Is the language and content of the measure culturally competent for your population?
Is the measure the right length?
YES
Sounds like the measure might be a good fit.
NO- Keep looking for something else. If nothing else exists- you might be able to justify using this
NO- See if there is something better, but if not, use this one.
NO- You generally should not make changes to a validated instrument, but if there is nothing better available, then you may make modifications.
