Thursday, February 3, 2011

How predictive dialing works

I gave a training this morning to a group of political organizers across the country on how to use Impact Dialing, as part of which I explained how predictive dialers work. That made me think that maybe it's time that I explained it as part of this blog, too.

If you're ever had a long list of phone numbers to call, you know that at best, only maybe one out of two people will pick up the phone. In the middle of the day on weekdays, it can be much lower, often less than one in ten. And even when somebody does pick up the phone, it takes at least a few seconds for them to answer.

Predictive dialing uses statistics to reduce both of these sources of delay. By observing what proportion of people are answering the phone, a predictive dialer dials multiple numbers every time someone becomes available. So if one 1 out of 4 people is picking up, the dialer will dial somewhere around 4 lines when a caller is available. Additionally, it will start dialing even before a caller is done with a phone call. If a typical call lasts 100 seconds and it takes people about 10 seconds to answer the phone, the dialer will start dialing at around 90 seconds.

All of this math is a gross simplification, but it gives you an idea of the advantages of predictive dialing. It should also give you a hint about the shortcomings: if the dialer guesses wrong and somebody picks up the phone unexpectedly, there will be no caller available to talk with them. These are called "abandoned" or "nuisance" calls. That's why, when you're calling a very valuable list (such as donors), it's often better to use a preview dialer that only dials a single line after you've finished your last call.

This math also hints at when predictive dialers are most effective. The law of averages states that any chance error gets smaller as the sample size increases, so the more people using a dialer, the more efficient it is. Similarly, the less variation there is in the lengths of the phone calls, the more accurately the dialer can predict when to make the next dials.

Impact Dialing is doing a lot of research into pushing the limits of predictive dialer efficiency, as well as even making preview dialing faster. This research is under wraps until we get it hammered out and patented, but I can't wait to share what we're working on.