Adding probabilities together

[Sunaj]

Just trying to wrap my head around some (very) basic math here by converting it into AU3 syntax, on this page (http://www.paulgraham.com/naivebayes.html) there is a good example of how to add two, or more, probabilities together. Here's the short version:

If a and b are the probabilities associated with two independent pieces of evidence [that someone is a basketball player], then combined they indicate a probability of:

       ab
-------------------
ab + ( 1 - a )( 1 - b )

So in this case our answer is:

         (.60)(.72)
-------------------------------
(.60)(.72) + (1 - .60)(1 - .72)

which is .794. There is a 79.4% chance that the person is a basketball player.

 

Now, any takes on how I would implement that simple math in autoit code? For now I've got:

$prbs = 0.60 + 0.72
$dividers = ((0.60+0.72))+((1-0.60)+(1-0.72))
$result = $prbs / $dividers
ConsoleWrite('$result: ' & $result & @CRLF)

And the output is "0.66" which certainly isn't right so I'm doing something wrong, any takers/helpers on this problem?

Edited December 16, 2013 by Sunaj

[BrewManNH]

ab = a * b, not a + b.

[Sunaj]

ab = a * b, not a + b.

Ah so simple, thank you. After writing code to accumulate/calculate conditional probabilities (in PHP) I was stuck on how to combine them, this solves it nicely (and makes a good case for learning a bit of basic math notation), here's the fixed code in case someone should stumble on this subject down the road:

$prbs = 0.60 * 0.72
$dividers = ((0.60*0.72))+((1-0.60)*(1-0.72))
$result = $prbs / $dividers
ConsoleWrite('$result: ' & $result & @CRLF)

[BrewManNH]

It's been a LOOONNNGGG time since I've sat in a math class, good to know I haven't forgotten everything yet.