Random vs Systematic Error

Question 1

Non-Differential misclassification

Answer 1

1. Also known as Random Error
2. Exposure or disease is misclassfied, but the misclassification does not depend on the status of another variable.
3. Misclassification of exposure DOES NOT differ among exposed with or without the outcome
4. Misclassification of outcome DOES NOT differ among those exposed or unexposed
5. Bias is always towards the null
6. Can occur in both exposure and outcome measurements
7. Can occur in either case-control or cohort studies ; both cases and controls or exposed and unexposed have same degree of error in classifying exposure or outcomes

Question 2

Differential misclassification

Answer 2

1. Systematic error
2. Estimates are inacurrate further away from the central true value
   3.Exposure or disease is misclassfied, but the misclassification depends on the status of another variable.
3. Misclassification of exposure is different among exposed with or without the outcome
4. Misclassification of outcome is different among those exposed or unexposed
5. Bias away from the null
6. Case-control study are prone to differential misclassification