Measurement properties, validity, reliability - Reliability and Responsiveness (vervolg)
5 important questions on Measurement properties, validity, reliability - Reliability and Responsiveness (vervolg)
What is the internal consistency (from domain reliability)
- The interrelatedness among the items
- Multi-item (or multi task) instrument/PROM
- Latent (non observable characteristics)
The steps to assess internal consistency
- Assess if there are different factors with a measurement tool -> factor analyses
- Asess inter-relatedness of items per factor -> cronbach's alpha
What is the reliability test retest design
- Inter rater
- Different raters on the same occasion
- Or even better: different raters on different occasions
- Intra rater
- By the same rater(s) (i.e., raters or responders) on different occasions
- Construct should not have changed between the 2 measurements: stability!!
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What is measurement error
SEM = standard error of measurement, standard deviation of repeated measurements in one person
SEM = (wortel) var (error)
What is a method of Bland and Altman
- Interval and ratio scale
- Measurement error is expressed in the same units as the measurements
- Limits of agreement
- d +/- 1.96 * SDd
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