Validity refers to how well a measurement tool measures what it is intended to measure. There are several types of validity: 1. Content validity measures how well the items on a tool represent the full scope of the concept being measured. It is assessed through expert ratings. 2. Construct validity examines how well a tool measures a theoretical construct or trait. It is assessed through factor analysis and hypothesis testing. 3. Criterion validity assesses how a measurement relates to outcomes on another tool measuring the same construct (concurrent validity) or future outcomes (predictive validity).

1. Summary
Validitytypes

2. Validity - Definitions
The extent to which a scale measures what it was designed to
measure.
Validity- In its purest sense, this refers to how well a scientific test
or piece of research actually measures what it sets out to, or how
well it reflects the reality it claims to represent.
Types
 Content validity
 Face validity
 Construct validity
 Criterion validity

3. Content Validity Index
• Minimum of 3 raters
• Not more than 10
• Rating of each item on a 4 point ordinal scale
1-Not relevant
2-Somewhat relevant
3-Quite relevant
4-Highly relevant

4. I - CVI
• CVI (I) = number of experts rating as relevant / total number of experts
• Acceptable CVI
– Items with CVI of 0.9 - 1 are acceptable
– Items with CVI of 0.8 – 0.9 are acceptable if the number of raters is
more than 5 but not acceptable if number of raters is less
S – CVI
• The proportion of items given a rating of 3 or 4 by both raters involved
– Universal Agreement
– Average

5. Content Validity Index

7. Content Validity
• The degree to which an instrument has an appropriate sample of items for
the construct being measured
Two approaches to content validity
 A priori efforts by the scale developer to enhance content validity through
careful conceptualization and domain analysis prior to item generation
 Posteriori efforts to evaluate the relevance of the scale’s content through
expert assessment
Expert Judges
Panel of experts rate individual items
Total score for each item computed and agreed cut off values used

8. Construct validity
• A hypothetical variable comprised of a set of component
responses or behaviours that are thought to be related
Multidimensional Fatigue Scale
General Fatigue
• I feel tired
Physical Fatigue
• Physically I feel
I am in a bad
condition
• Physically I am
only able to do a
little
Mental Fatigue
• My thoughts
easily wander
• It takes a lot of
effort to
concentrate

9. Construct validity
• extent to which the scale captures the specific
theoretical construct.
How is construct validity measured?
• Structural validity
• Hypothesis testing
Structural Validity Assessment
• The analytical foundation for evaluating an instrument’s
dimensional structure is through factor analysis
• Exploratory and Confirmatory Factor Analysis

12. Hypothesis testing
• A scale which has construct validity should fit into hypothetical
relationships that explain the construct
Example:
• Trust in physician is influenced by shared identity,
physician’s behaviour, personal involvement and comfort

14. What is criterion validity?
• The extent to which a measurement with a scale relates to outcomes in
the form of
– Measurement using a different scale
– Other clinically relevant outcomes
Concurrent Validity
• The construct of interest is measured using two scales concurrently
• One of these is assumed as a gold standard scale
• Example
– A new scale was developed to measure physical activity levels
among adolescent school going children
– The scale was administered concurrently along with the GPAQ
scale (gold standard)
– The new scale score and the GPAQ scores were compared
concurrently

15. Predictive validity
• The extent to which the score on a scale predicts scores on
some criterion measure
– Whether scores on NEET entrance exams predict the first
year MBBS semester exam scores?