Time Windowing
Time windows are more than just the solution to left truncation. They are a powerful technique for other purposes. This section investigates time windows in general and some ways to use them.
A Business Problem
Once upon a time, a mobile phone company was developing a forecasting application using survival analysis. This type of application was discussed in the previous chapter, and forecasting can be a powerful application of survival analysis. They provided a large amount of data for tens of millions of customers early one May for a proof-of-concept. The schedule called for the proof-of-concept to be reviewed in the summer, steadily improved upon, and then the final forecasting project would begin at the end of the year. So, using historical data, the proof-of-concept began that May.
In April, a shrewd person in finance decided to change one of the company’s policies, just a little tweak actually. The old policy was to disconnect a customer on the date the customer...