Probability spreadsheet

[PhilHibbs]

I've made a spreadsheet that calculates probability of success in opposed tests. I've mentioned it before, but it's now in a nice usable state. It's an OpenDocument spreadsheet that I made with LibreOffice.
http://dl.dropbox.com/u/8129635/OpposedTests_v1.01.ods
Put the two opposed skill percentages in the blue highlighted cells on the first sheet. These values propagate through to the other sheets.

The first two sheets calculate the chances of success using "lower is better" and "higher is better" respectively, just to show the difference that it makes. The next three sheets show the chances where the attacker has a +10 to their skill, or if the +10 is applied retrospectively to the defender's resistance (e.g. the Rune Touched Mastery ability, if it is not applied as a bonus to the spell caster's chance to cast the spell in the first place). These sheets are not of very much general interest, but they're there because it came up in my game.

Outcomes in the 100x100 grid are highlighted in green if they result in the attacker "A" winning.

The green highlighted percentage chance in Cell B2 is the chance of the attacker "A" both succeeding their skill roll and beating the defender "D". The yellow percentage chance in Cell B3 is the chance of the defender beating the attacker once it has been established that the attacker has succeeded - for instance, the chance of the defender making a Resilience roll against damage inflicted, or the chance of making a resistance roll against a spell that has been successfully cast.

 

[simonh]

Executive summary?

 

[PhilHibbs]

Executive summary?

For example:
1. 60% spellcasting skill vs 40% Persistence. The caster has a 52.17% chance of both casting the spell and overcoming the enemy's Persistence (% chance in green). From the target's point of view, once the caster has successfully cast his spell, the target has a 13.05% chance of making his Persistence roll and beating the caster's success (% chance in yellow).

2. 80% spellcasting vs 55% Persistence. The caster has a 64.72% chance of casting the spell and overcoming the enemy's Persistence. From the target's POV, once the spell is cast, he has a 19.1% chance of resisting the spell.

3. 40% spellcasting vs 35% Persistence. The caster has a 33.85% chance of casting the spell and overcoming the enemy's Persistence. Once the spell is cast, the target has a 15.38% chance of resisting.

The two percentages are independent - the 33.85% chance in the last example takes the 15.38% resist chance into account already.