CK030 - Accelerated Failure Time Model

Question 1

What is the formula of the ‘accelerated failure time (AFT) model’ ?

Answer 1

log(T) = b0 + b1x1 + b2x2 + …

Question 2

What are the assumptions of the ‘AFT model’ ?

Answer 2

• Linearity
• Additivity
• Error terms distribution

Question 3

What is the most important assumption for the ‘AFT model’ ?

Answer 3

The error terms distribution

Question 4

What is the interpretation of the coefficients in an ‘AFT model’ ?

Answer 4

A 1 unit increase in x corresponds to:
- A b change in the average log(T)
- Multiplies average T by a factor of exp(b)

Question 5

How to check for the ‘error terms distribution’ ?

Answer 5

Compare the Kaplan-Meier curve of the residuals (so residuals instead of time) and compare this to the Kaplan-Meier curve of the error terms (so from the assumed distribution)