Lynata wrote:That being said, given how deadly this effect can be on lower level characters and enemies, perhaps a houserule that adds a +1 bonus after each failed test would help? This way, in the 1st round of stun the test would be 9.26%, in the 2nd round 16.2%, in the 3rd 25.92% and so on...

The cumulative probability of making a TN 15 test, then a TN 14 test, then a TN 13 test is (given a +0 modifier) actually 43.7% (9.26 + 14.7 + 19.71 = 43.68)

You sure you didn't accidentally use the numbers from the series without any +1 bonuses? (I.e. the 9.26, 8.40, 7.62 series making up 25.29 - I note that your 25.92 could be the same number only with two figures jumbled)Anyway, you all might jump at the rather larger chance - 44% instead of 25%, a difference of 19 percentage units or an seventy-five percent increase - but this is because of the specific shape of the 3d6 bell curve. A +1 bonus is very valuable when the slope is steep, as it is in this case. Contrast with either the case when Constitution is not 0 but -2 or +2 instead...

Con -2 without the cumulative +1 bonus (three TN 17 tests): 1.85+1.82+1.78=5.45

Con -2 with the cumulative +1 bonus (a TN 17, a TN 16 and a TN 15 test): 1.85+4.54+8.67=15.1

The difference is 9.65 percentage units; the probability might be tripled but goes from a very low number to a slightly larger but still low number.

Con +2 without the cumulative +1 bonus (three TN 13 tests):25.93+19.20+14.23=59.36

Con +2 with the cumulative +1 bonus (a TN 13, a TN 12 and a TN 11 test):25.93+27.78+23.15=76.85

The difference is 17.5 percentage units; this is an increase by only thirty percent.

By this I only mean to say that the bonus makes a big impact on the example discussed but not necessarily as big an impact when the numbers are different. (AGE is decidedly different than D&D here - even though both games operate on roughly the same 3-18 scale a +1 bonus is always equally valuable in all D&D cases, where the utility differs greatly in AGE)

Zapp

PS. For unparallelled probability calculating power, do use

Troll. This tool really stands head and shoulders above anything else in the way of dice calculators.