On the subject of probabilities Options

[Demerzel]

Over in the edge thread there was some talk of probabilities in SR4 and I’ve got a few charts I’ve set up for non-edge cases to give an idea of chances. Links:

Opposed Tests With Standard Dice Pools
Opposed test table
Opposed test chart

Standard Dice Pools
Exact hits on a standard dice pool
Meeting a threshold on a standard dice pool

Rule of Six Dice Pools
Exact hits on a Rule of Six dice pool
Meeting a threshold on a Rule of Six dice pool
Chart for Meeting a threshold with RoS


They may not really be useful but I thought they were a little informative. The chart I called a spectrum is probably not the best name for it. It’s really a contour plot, where the numbered isopleths refer to the defenders dice pool, along the x-axis is the attackers dice pool, and the y-axis is the percentage probability that the attacker will generate at least 1 net hit.

I’ve played with, but haven’t really generated a similar chart for edge with the rule of sixes.

EDIT: Changed the links a little, and added some tables

Enjoy,

[hyzmarca]

I do believe that fractions are better than decimals for such charts. Some of the roundings done give incorrect impressions, specifically where the probabilities round to zero.

[Demerzel]

I'd be interested in seeing any example of a statistics text or book of mathematical tables that would endeavor to put a binomial distrobution such as this into a table of fractions. Formating a chart like this with fractions rather than decimals would be insane.

When you're doing an individual calculation in some cases it may be beneficial to give an exact fraction, but this is not a good example in my opinion.

It would perhaps be more like the tables you'd find in a book of mathematical tables if I were to put it out to four decimal places, but I wanted something that could be referenced in a room lit for ambiance rather than table lookup.

I considered the issue of 100 and 0 being poor elements to leave in a chart. That is specifically why I choose to use one decimal accuracy, since it would imply (at least to a FORTRAN programer, and hopefully to anyone with a math/science background) that it is not an integer.

[dionysus]

The spectrum graph interests me: I'm reading that equal dice pools give the defender about a 20% advantage, is that correct? This is because defenders win ties?

[Demerzel]

Yes, defenders win ties. That 20% diminishes with increased pools however. Someday I may generate another table that includes ties. But that is only really of use in those rare cases you're using touch attacks. Since they don't come up often in my games it's not so much of a problem.

[Protector152]

i like the idea that i can use thease tables to predict how a test will come out. do you think you can also put out a glitch series and maybe include cursed/gremlins in it?

[Garrowolf]

I thought that ties were a light hit now and not going to defender anymore in SR4.

[Mistwalker]

Ties are a grazing hit, causing no damage.
But, if there is something else to the attack, like shock gloves, those still take effect.

[Garrowolf]

Okay one of the things I was thinking about is that Thresholds are harder on the roll then dice pool penalties. If you want to make an effect harder then increasing the threshold is better.

How much of these dice pool penalties could make more sense as a threshold?

I was thinking about range as a good start.

[Mistwalker]

One of the rule tweaks, page 69? has something similar, with thresholds for ranged combat.

[Demerzel]

[Moon-Hawk]

Also drawing off the other probability thread, I'd be interested to see those first two tables redone using edge and rule-of-six.
Then you could look at one table and say "I have x chance of success, but if I add edge dice (looking at the other table) my chances go up to y. That is/isn't worth spending edge on."

[Jaid]

well, i guess you can at least know for a fact that your work is appreciated demerzel... people can't get enough of it :P

while you're at it, could you develop a program that will do my income taxes, calculate the probability of any investment i make being profitable (and also by how much) and can build a robotic version of me that will do my job but give all the money to me? :P :D

[Moon-Hawk]

And I want a pony. A unicorn pony. With wings. A pink one.
If it's not too much trouble.

[Mistwalker]

I only want a few books.

The sports almanacs for 2007 to 2070.

I won't even complain if they are on CD or memory stick

[Demerzel]

Pink Winged Unicorn Costume

You'll just need that and a baby to put in it. You'll have to find someone else to help you make one of those.

[Moon-Hawk]

O...
M...
F...
G
I ask for a pink, winged, unicorn pony and 35 minutes later you deliver. Awesome. I am stunned.

I have a baby-maker, but I don't want to use it yet. I think I'd need a cage or something to put the baby in, and I just don't have room for another terrarium in my apartment right now. ;-)

[Demerzel]

I do have a table of values for edge dice, I just didn't put it up here. It is only for the case where you add edge to the pool beforehand however. Generating a table for the cases where you roll, get a result then decide to add edge or reroll faiures felt like too large of a headache. But perhaps I'll look into it.

[Moon-Hawk]

Yeah, but the first one is the only one that really requires it's own table.

As we talked about in the other thread, if you're adding dice or rerolling failures, you've likely already rolled the first time so you know how many dice you're rerolling, so just use the existing tables with a smaller dice pool to figure out how many successes you'll be adding to what you already have. It really doesn't require its own table.

[Demerzel]

True, I probably won't have it up for a bit though. It's on the home PC. Perhaps I'll try and upload it at lunch.

[HeySparky]

[MaxHunter]

hey demerzel, your sig link has expired...

I would have thought you were into linguistics, not math!

cheers,

Max

[Demerzel]

Gah! I knew I wasn't supposed to delete that. I cleaned out my personal webspace when I put up those charts for this thread. Should work now.

[Demerzel]

Just to whet some appetites, I've put together some charts for dice with rule of six applied, I'll PDF 'em up and post them sometime this afternoon. I hope.

[Moon-Hawk]