# Lookup Model for Probability of Response

This section considers a different sort of problem, related to the subscription data. *What is the probability that a customer who starts in 2005 is going to last for one year*?

## The Overall Probability as a Model

The way to start thinking about this problem is to consider all customers who start in 2004 and ask how many of them survive for exactly one year. Using one year of starts dampens seasonal effects occurring within a year. Also, the subscription table has no stops prior to 2004, limiting how far back in time we can go.

Chapter 8 addressed several different methods for looking at survival and retention. This section looks only at the point estimate after one year, as calculated by the following query:

SELECT AVG(CASE WHEN Tenure < 365 AND StopType IS NOT NULL THEN 1.0 ELSE 0 END) as stoprate FROM Subscribers WHERE YEAR(StartDate) = 2004

Customers who stop within one year have tenures less than one year and a non-NULL stop...