The Validities
Clinical Café By Sarah Sweeney James, MS, CCC-SLP
The report flew off of the printer just minutes before the family arrived. As the ink dried you embarked on your very articulate briefing of the results and interpretation. All seemed to be going smoothly as evidenced by eye contact and head nods from interested parties, and then that question, the one question that caught you off guard on that particular Monday morning…
“Why did you choose this test? Is it valid for what we need? And how do you know?”
As a drip of sweat formed and you thought that things couldn’t have grown more taxing, your supervisor chimed in with, “We pride ourselves on choosing well developed assessment tools which meet individualized evaluation needs of each student that we test. Ms. SLP please discuss this test’s development as well as its validity.”
You groped for the information that was the heart of a paper written a touch more than ten years ago, a sea of words did the wave through your brain: validity…reliability…content… internal…criterion…external – “hmmm, what should I go with here??” you thought.
That’s fiction! An imaginary tale, just some creative writing, you say? No! Concerned parents, administrators, supervisors, attorneys, judges and many others have increasingly posed this very question.
Would your answer reassure the questioner?
Don’t: run down the basement, drive to your storage facility or race to your garage in search of those boxes, the ones labeled: “grad school – keep forever.”
Do: refer to specific test manuals for in-depth information about their validity and keep reading for a short and snappy review on what are affectionately (by whom??) known as “the validities.”
Generally Speaking: A Definition
“The general concept of validity…defined as “the degree to which a test measures what it claims, or purports, to be measuring” (Brown, 1996, p. 231).
“Validity is the most important consideration in test evaluation. The concept refers to the appropriateness, meaningfulness, and usefulness of the specific inferences from the test scores. Test validation is the process of accumulating evidence to support such inferences (Goldstein & Zedeck, 1985, p. 9).”
Specifically Speaking: Content, Construct, Criterion, Clinical
Content Validity
Content validity is concerned with a test’s ability to represent all of the content in a particular area, not just the content in the test questions themselves. Potential test questions should be reviewed by established content experts who must decide: are these test questions representative of the subject matter as a whole and can an inference be drawn from this test score to a large domain of items similar to those on the test?
Real Life Example
Peabody Picture Vocabulary Test-Third Edition (PPVT-III)
It would be too voluminous and insurmountable for the PPVT-III to include all possible receptive vocabulary words at each age or grade level; therefore, the content experts have chosen words that represent the larger domain of receptive vocabulary to be included on the test.
When a test demonstrates first-rate content validity, the examiner can be confident that the test score is more than just a measure of the specific content of the test’s (216 words), but can be generalized to a larger domain of content (receptive vocabulary).
Construct Validity
Construct validity refers to the degree to which a test is measuring the construct it claims to be measuring.
A construct is an attribute, proficiency, ability, or skill that happens in the human brain. For example, overall English language proficiency is a construct.
Real Life Example
Expressive Vocabulary Test (EVT)
In order to exhibit solid construct validity, the EVT must measure expressive vocabulary, not receptive vocabulary, articulation, phonemic awareness or any other speech or language skill.
Goldman Fristoe Test of Articulation (GFTA)
In order to exhibit solid construct validity, the GFTA must measure the production of the sounds of the English language (articulation), not expressive vocabulary, receptive vocabulary, phonemic awareness or any other speech or language skill.
Criterion Validity
Criterion validity measures the correlation of the test being validated with some well-respected outside measure(s) with the same objectives or specifications.
Real Life Example
Test for Auditory Comprehension of Language-Third Edition (TACL-3)
To show evidence of high quality criterion validity, the TACL-3 must report correlations with other measures of auditory comprehension.
A tester should be able to expect that when compared, assessment tools examining the same or similar construct (auditory comprehension in this example) would produce scores within the same range of performance.
Clinical Validity
Clinical validity information includes the ability to compare test performance between and within clinical subgroups. Clinical subgroups include individuals who are exceptional in some way. Examples include persons who are gifted and talented or demonstrate a reading disability, hearing impairment or articulation disorder. In order for an assessment tool to have clinical validity, persons in clinical subgroups must be included in the standardization process.
Real Life Example
Expressive Vocabulary Test (EVT)
Johnny, a sixth-grader diagnosed with a reading disability was given the EVT and scored significantly lower than his age and grade peers in the normative sample. However, when compared to the reading disabled clinical subgroup, his scores were found to be close to the average of that group. Again, let’s refer to a specific study in the manual.
Stay-tuned for more specific information on each of the validities!
References
www.speechandlanguage.com
Brown, J. D. (1996). Testing in language programs. Upper Saddle River, NJ: Prentice Hall Regents.
Standards for educational and psychological testing. (1985). Washington, DC: American Psychological Association.
