Measurement Error and Misclassification

Question 1

What are the 4 categories of clinical variability?

Answer 1

1. Between-person biological variability
2. Within-person biological variability
3. Between-observer measurement variability
4. Within-observer measurement variability

Question 2

What is kappa (K) a measurement of?

Answer 2

Reliability for categorical or qualitative data. Corrects the degree of chance in the overall level of agreement. Closer to 1 means closer agreement.

Question 3

How is kappa calculated?

Answer 3

Actual agreement beyond chance/potential agreement beyond chance

Question 4

Which has more impact on the OR, misclassification of outcome or exposure?

Answer 4

Misclassification of exposure has more outcome than misclassification of outcome because:
1. Most of the problems with misclassification occur with
respect to exposure status, not outcome.
2. There are a number of mechanisms by which
misclassification of exposure can be introduced, but most
outcomes are more definitive and there are few
mechanisms that introduce errors in outcome.
3. Most outcomes are relatively uncommon.
4. Misclassification of outcome will generally bias toward the null, so if an association is demonstrated, if anything the true effect might be slightly greater.