Reliability or Validity

Reliability or Validity

Reliability gets more attention: Easier to understand Easier to measure More formulas (like stats!) Base for validity

Need for validity

Does test measure what it claims? Can test be used to make decisions?

Validity

Reliability is a necessary, but not a sufficient condition for validity.

Validity: a definition

“A test is valid to the extent that inferences made from it are appropriate, meaningful, and useful”

Standards for Educational and Psychological Testing, 1999

“Face Validity”

“looks good to me”!!!!!!!

Trinitarian view of Validity

Content (meaning) Construct (meaning) Criterion (use)

1) Content Validity

“How adequately a test samples behaviors representative of the universe of behaviors the test was designed to measure.”

Determining Content Validity

describe the domain specify areas to be measured compare test to domain

Content Validity Ratio (CVR)

Agreement among raters if item is: Essential Useful but not essential Not necessary

2) Construct validity

“A theoretical intangible”“An informed, scientific idea”

-- how well the test measures that construct

Determining Construct validity

behaviors related to constructs related/unrelated constructs identify relationships multi trait/multi method

Multitrait-Multimethod Matrix

Correlate scores from 2 (or more tests) Correlate scores obtained from 2 (or more)

methods

Evidence of Construct Validity

Upholds theoretical predictions Changes (?) over time, gender, training

Homogeneity of questions (internal consistency, factor or item analysis)

Convergent/discriminant Multitrait-multimethod matrix

Decision Making

How well the test can be used to help in decision making about a particular criterion.

Decision Theory

Base rate Hit rate Miss rate False positive False negative

3) Criterion Validity

“The relationship between performance on the test and on some other criterion.”

Validity coefficient

Correlation between test score and score on criterion measure.

Two ways to establish Criterion Validity

A) Concurrent validityB) Predictive validity

Determining Concurrent validity

Assess individuals on construct Administer test to lo/hi on construct Correlate test scores to prior identification Use test later to make decisions

Determining Predictive validity

Give test to group of people Follow up group Assess later Review test scores If correlate with behavior later can use later

to make decisions

Incremental validity

Value of including more than one predictor Based on multiple regression What is added to prediction not present with

previous measures?

Expectancy data

Taylor-Russell Table Naylor-Shine Tables Too vague, outdated, biased

Unified Validity - Messick

“Validity is not a property of the test, but rather the meaning of the scores.”

Value implicationsRelevance and utility

Unitarian considerations

Content Construct Criterion Consequences

Threats to validity

Construct underrepresentation (too narrow) Construct-irrelevant variance (too broad)

construct-irrelevant difficulty construct-irrelevant easiness

Example 1

Dr. Heidi considers using the Scranton Depression Inventory to help identify severity of depression and especially to distinguish depression from anxiety. What evidence should Dr. Heidi use to determine if the test does what she hopes it will do?

Example 2

The newly published Diagnostic Wonder Test promises to identify children with a mathematics learning disability. How will we know whether the test does so or is simply a slickly packaged general ability test?

Example 3

Ivy College uses the Western Admissions Test (WAT) to select applicants who should be successful in their studies. What type of evidence should we seek to determine if the WAT satisfies its purpose?

Example 4Mike is reviewing a narrative report of his

scores on the Nifty Personality Questionnaire (NPQ). The report says he is exceptionally introverted and unusually curious about the world around him. Can Mike have any confidence in these statements or should they be dismissed as equivalent to palm readings at the county fair?

Example 5

A school system wants to use an achievement battery that will measure the extent to which students are learning the curriculum specified by the school. How should the school system proceed in reviewing the available achievement tests?

Example 6

Super sun computers needs to hire three new employees. They have decided to administer the Computer Skills Assessment (CSA) to their applicants and use the results as the basis of their decision. How can they determine if that measure is a good fit for their hiring practice?

Project homework question What content or construct is your measure

assessing? (explain your answer) What do you think congruent and discriminate

constructs would be to the one in your measure? How would you determine the content or construct

validity of your measure? How would you determine the criterion validity of

your measure? Why would you use those approaches?

Project homework question

Select a standardized instrument from MMY to use as a comparison for your measure?

Copy the relevant data. Why did you select that instrument? How would you use it to help standardize

your measure?