Skill success probabilities

[Angaros]

Hi folks! I'm wondering if anyone has made any statistical calculations regarding skill successes? I've been doing some calculating on my own, but I'm not entirely sure if the outcome is correct -- mostly because I don't like where it's going. According to my results skill tests and attribute tests are too easy to succeed with in TRoS. With an attribute of 4 and TNs of 4, 6, 8 and 10, the chance of scoring at least one success is about 99, 94, 76 and 34% respectively. The rulebook stated that 6 is an average TN for attribute tests, it also says a skill TN of 7 equals a trained professional (>=1 success chance with 4 dice vs TN 7 is 87%). IMHO this is a bit high as the average attribute level is 4 and many skills even at the beginning of a campaign could drop down towards TNs of 6 and 7. An easy fix would be to allow attributes of 1-5 instead (more or less halving attributes from the rulebook) like in WhiteWolf's games. It must be said though that I haven't gamed TRoS yet (probably will do some mock combats this weekend - yay!), but figures such as these still alarm me somewhat. Ofc, it might turn out that when I play the game I won't even notice this - the problem only occurs when performing attribute or skill tests solely versus TNs. When comparing successes with an NPC, the characters are on equal terms....

So - has anyone else given this a thought or two? What are your thoughts on the results? Do they matter at all?

[Lance D. Allen]

Skilled characters with a 6 or better tend to do well, but failure is still a looming option. Remember that a single success is still only marginal, and if there is a threshold to overcome, such as an opponent's successes, a single success isn't going to do any good.

Which is to say, skill checks are not remarkably easy to succeed, nor remarkably difficult, on average.

[ruusu]

There's a probability calculator on the RoS website, if I recall correctly. I have not had problems with skills - after all, you would expect a trained professional to succeed in an average task most of the time (that 87% sounds about right). It's more of a question of how good a success it is, as in how many successes were rolled.

And besides, rolls are modified by reducing or adding dice, so in difficult conditions you might be rolling 2 dice instead of the average 4. In the dark and during a thunderstorm that trained professional has a fairly high chance of failing in his task (this is where my math fails me, and so I cannot give you a percentage...)

Juho

[Brian Leybourne]

Look at it like this.

With a TN of 6, you have a 50/50 chance per die of succeeding. That means that with 2 dice you have a 75% chance of getting a success, with three dice 87.5% and with four dice 93.75%

But that's your chance of ONE success. Remember that the number of successes is important in TROS. And, as someone else pointed out, modifiers change the number of dice, not the TN.

The best advice I can give is that you try it out. You'll find that it works in play. The other very important note is that, frankly, I often don't bother to get PC's to roll if they're unopposed (this is, in essence, the rule of Jared). Unless it's going to advance the story if the PC slips and falls while he's trying to jump from one rooftop to another, I just let him do it without a roll. When I require rolls mostly is when the outcome is very important story-wise and usually that means it's opposed as well. And in an opposed roll, one success wont get you far.

Brian.

[Angaros]

Thank you all for the advice.

Brian: Your calculations are not entirely correct. The numbers I gave was for a minimum of one success, but I get your point though. However, demanding additional success dramatically changes the odds. More so than adjusting the number of dice (which is the method I prefer).  For example, throwing 4 dice versus a TN of 6 gives you a chance of 93.75% of scoring 1 succes, 68.75% chance of scoring 2 successes, 31.25% chance of scoring 3 successes and 6.25% chance of scoring 4 successes. The differences are pretty big IMO. But then again (as I've understood it) TRoS never was intended to give room for great detail in these areas, which is one reason why I like it.  This is of course an important point to be aware of when criticizing as I do.

Again, thank you for the tips. I've scheduled a test session with the gang this friday and I'll be sure to try your suggestions out. :)

[Morfedel]

The great thing about this method is you could interpret difficulties in three seperate ways:

1) Require more than 1 success

2) Subtract Dice

3) Add to the difficulty

or any of the above in any combination.

This means that you can play around with the probabilities any way you feel like, and have fun doing it:

"So, you want to leap over the chasm while playing a fiddle and avoiding arrow fire? Ok, you will need 3 successes, subtract 2 dice, and increase your TN by 4...."

Anyway, just a thought. :)