Re: [Dspam-user] Meaning of Confidence value

[Tom H. <to...@wh...>]

On 01/10/10 12:42, Julien Vehent wrote:
> Hi there,
> 
> I was browsing the code to understand the value of X-DSPAM-CONFIDENCE and I'm not sure I understand its meaning completely.
> 
> --- libdspam.c ---
>   /* Calculate Confidence */
> 
>   if (CTX->algorithms & DSP_MARKOV) {
>     if (CTX->result == DSR_ISSPAM)
>     {
>       CTX->confidence = CTX->probability;
>     }
>     else
>     {
>       CTX->confidence = 1.0 - CTX->probability;
>     }
>   } else {
>     if (CTX->result == DSR_ISSPAM)
>     {
>       CTX->confidence = rob_result;
>     }
>     else
>     {
>       CTX->confidence = 1.0 - rob_result;
>     }
>   }
> ------------------
> 
> As I understand the code, if a message is a spam, confidence = probability. If the message is a ham, confidence = (1 - probability).
> How does that gives an information on the level of maturity DSPAM has reached ?
> 
> Thanks,
> Julien
> 

Probability is the 'chance' that  a message is spam. A very low
probability means that a message is innocent. The lower the probability
is, the more confident DSPAM is that the message is innocent.

For example:
- probability=0.99 means 99% confident that a message is spam.
- probability=0.01 means 1% confident that the message is spam, or 99%
confident that it is innocent.

The calculation is there to make the confidence number have the same
value for both ham and spam: DSPAM is equally confident, but on a
different decision.

Regards,
	Tom