Okay so I never really though about proc rates before cause I thought I knew how they worked, but I just got into an arguement with a fleet mate about them and now I don't know anymore. Maybe you guys can clear this up.

My thoughts were that each weapon normally has a 2.5% proc rate for its added effect. Power drain for polaron, subsystem targeting for phasers, and so on and that each time you attack with that weapon you have a 2.5% chance to trigger it. So with 4 phaser weapons you would have 4 chances at 2.5% each. He claims that having four phasers makes the proc rate 10% each time you fire all of your weapons. He's adding them up as if the proc isn't for each individual weapon, but for all weapons combined once.

What is right? I'm using 5 polarized tetryon beam arrays(10% proc) on my tank and he says its the same rate as if using 5 regular tetryon beam arrays(2.5% proc). Is this true?

Each weapon has an individual chance to proc during its firing cycle. The percentages don't 'stack' across weapons.

*Edit* and if your Fleet-mate's logic was correct, your 5 x Polarized Tets would have a 50% proc chance no?

Actually I double-checked and the chance to proc is per-volley - hence some people prefer weapons that fire more often for the increased chance-to-proc (usually outweighed/negated by the slower weapons doing more overall DPS though).

*Edit* lol! Triple-checked - my first statement was correct - chance-to-proc is per-cycle meaning all weapons types have the same chance to proc within a given cycle. More info here.

Yes, that write-up is absolutely correct. Since each weapon is being checked for proc activation each time they shoot, the chances of any proc activating does go up as more weapons become involved. You can use the binomial formula below to get exact numbers:

http://www.stattrek.com/online-calculator/binomial.aspx

For example, if you shot a single phaser turret at a target, the odds of getting a proc is exactly 2.5%. If you shoot 8 phaser turrets at a single target at the same time, the chance of any proc activating is raised to 18.33% where Cumulative Probability: P(X >= 1). You will NOT see this by mousing over a single phaser turret involved since this is a cumulative probably taking into account all 8 phaser turrets shooting together.

Did you check that before they added the immunity to the phaser proc? I would have expected you to use disruptors or maybe polarons for a test like this, since they don't have an immunity and still have a clearly visible effect. With phasers, I'd be concerned that you missed attempted procs that occurred during the immunity.