False Positive Rate

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Hi hoping someone can give some advice

I look after a predictive dialler for an outbound call centre and have been try to work out our false positive rate.

We have trunk side recording and I have listened to 1000 calls which the dialler gave the outcome of Answer machine, out of those 1000 5 were not answer phones

can anyone advise what calculation they use to work out their false positive

Thanks in advance


Telemarketing Manager


I would assume that the false positive rate is 0.005% which is fantasic. Out of interest, how many were silent calls?


Telemarketing Manager


To follow up on that, Jonty has some great info on this under, A beginners guide to the Ofcom regulations.

• The consultation suggested that companies using AMD need to factor AMD “false positives” into their abandoned call rate by subtracting AMD calls from the number of calls categorised as being passed to a live operator. AMD ‘calls’ are calls answered by an answer machine and correctly identified as such; these should not be included in the abandoned call rate calculation.

•With regard to AMD, Ofcom has not stated a specific false positive rate. However, in the course of an investigation, the onus will be placed on the user to demonstrate the basis and evidence on which an estimate has been made and would likely require practical testing.

Regards abandoned calls rates

•Abandoned call rates must not exceed 3% of live calls for any 24-hour period for each campaign. Unanswered calls must ring for a minimum of 15 seconds.

•Records must be kept to demonstrate compliance with these requirements.

So I would say in summary that you would need to add the 5 False positives to your abandoned call rate and as long as its below 3% and you can demonstrate compliance with these requirements, you should be fine.


Personally I don't believe any outbound operation should be using AMD for a host of reasons, not least because it's almost impossible to remain compliant while doing so.

Your sample of 1,000 calls simply isn't big enough to allow you to demonstrate that you've made a concerted effort to determine what your false positive rate is. That is only a fraction of the answer machines I'd suggest on a daily basis. Even in best conditions testing some of the largest dialler vendors can only achieve an accuracy rate of around 97% to 98%. The calculation is simple. Let's say you get 20,000 answer machines a day, have a false positive rate of 2%, that is 400 abandoned calls you have to take into account and add on.


Dialler Manager

Hi Jason,

5 out of 1,000 would be 0.5% FP rate, not 0.005%. Sloppy maths.

Hi Garth,

It is very easy to stay compliant using AMD, you just need the right tech. and the right people to operate it. OfCom acknowledge their awareness of the existence of tech. that can achieve a 0.5 FP rate in their September 2008 statement and things have moved on considerably since the acknowledgement of those claims.

My dialler averages 25,000 dials per day, 1 abandoned call and 0 false positives.

Compliance is not a problem and it would be hard to argue that there are any ethical issues with stats. like these. Do you have any reasons other than compliance and ethics for not believing any outbound operation should be using AMD?

Hi Andy,

Here is a link - http://stakeholders.ofcom.org.uk/consultations/persistent_misuse/statement/

Study the documentation there. If you find it to be ambiguous in any way, contact OfCom directly (details are on their site). When it comes to clarification of regulatory guidelines it is best to go direct to the source, rather than to an open forum, to determine correct action.



Telemarketing Manager



Thanks for the correction, I had noticed, but didnt see the need to correct myself, I'm thankful that you did. I dont think anyone has told me my Maths is sloppy since I was at School.


Dialler Manager

Good times.



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