Lecture 7: Validity, Accuracy, Sensitivity and Friends Flashcards
What is validity?
The extent to which a method gives you the “correct” answer i.e. measures what you want it to measure
What is absolute validity?
the extent to which a measurement or method accurately reflects the true value or reality of what it is intended to assess, without bias or error
What does the reference method require for absolute validity?
Reference method requires discreet or hidden observation or recording of what a person consumes, without their awareness, to ensure accurate and unbiased data
What is relative validity?
the degree to which the results of one measurement or method agree with those of a reference or gold-standard method, rather than directly reflecting an absolute true value
What is the reference method for relative validity?
Reference method is another indirect method of assessing intake
What is repeatability?
The extent to which a method gives you the same answer each time you use it
What are issues to consider in an FFQ “validation” study?
- Appropriate reference method
- Study sample
- Timeframe
- Methods
What is accuracy?
Describes the extent to which the measurement is close to the true value
What is measurement error?
Difference between measured value and true value
What is the observed intake equation?
observed intake = true intake + measurement error
What are the two types of measurement error?
- Random error
- Systematic error
What does measurement error lead to?
- Attenuation of relationships
- Bias
What is random error due to?
Chance or normal variation
What does’t random error change?
The mean
What does random error increase?
Variability around the mean (stretches the tails)
What does random error decrease?
Reproducibility
What are the main sources of random error?
- Daily variation in consumption
- Inaccurate portion size estimation