W9 - Reliability & Validity Flashcards
Define reliability
Consistency of measurements, an ind’s performance on a test or the absence of measurement error.
Classical Test Theory
Spearman 1904
O = T + e
O = Observed score T = True score e = Error
What are the 2 types of error measurement?
Systematic error
Random error
Define systematic error
Consistent error which biases the true score + doesn’t affect reliability
Define random error
Unpredictable error which biases the true score + does affect reliability
Ways to minimise error
Train researcher to ensure proficient use of instrument
Repeats
Compare data from 2+ researchers
Careful design of study protocol
Consider choice of instrument
Calibrate instrument
Common technique used to assess relative reliability across time/researchers/writers…
Pearsons correlation coefficient
Higher correlation = ⬆️ reliability
How can relative reliability be assessed?
Through the test-retest reliability
= Assess the stability of the measurements on different occasions.
What is used when doing the test-retest reliability?
2 tests: Pearsons correlation coefficient
2 or + tests: Intraclass correlation coefficient (ICC)
Inter-rater reliability
Reliability / consistency across raters
Correlating the scores obtained from a group of participants by 2 or + researchers
What does internal consistency stand for?
Reliability across different parts of a measurement instrument
i.e items within a sub-scale on a questionnaire
How is internal consistency assessed?
Using Chronbach’s alpha reliability coefficient
Values range from 0-1
Closer to 1 = higher reliability
List some terms used for absolute reliability
Also known as measures of absolute reliability
Technical error of measurement
SE of measurement
Coefficient of variation
Limits of agreement
Define validity
Extent to which a test/instrument measures what its supposed to measure.
What are the types of validity?
Validity of measurement
Validity of a study
What comes under validity of measurement?
Face validity
Content
Construct validity
Criterion
Validity of measurement
What comes under criterion validity?
Concurrent
Predictive