(This question is inspired by by Neil Slater's answer here: What are the acceptable limits for questions using the probability tag?. Other related questions are: Rules for increasing ability scores in Basic D&D?, Help Needed With Probability Math for 2d10, and this one on SE.Mathematics)
In my OSR game, I implemented two different systems for increasing attribute scores. Every four levels, the characters get to choose one ability score to increase by a point. (This was stolen whole-cloth from D&D 3.X) I also implemented a fractional ability score system. (This was stolen from Unearthed Arcana.) Each ability score has a fractional rank from 0 to 100. When you level up you roll 2d10 to generate a number from 2-20 and add that to the fractional ability score. When that gets to be 100, it resets and the ability score goes up by a point. (To be clear, there are six dice rolls involved for just this rule.)
So far, so good. The PCs have gained a couple of levels and recorded their fractional totals. However, I looked into the math for the fractional ability scores and realized that it's going to take a long time for the PCs to make any progress with it. The specific numbers:
- Upon reaching 9th level, there's a 15% chance that a fractional ability score has gone up by a point.
- Upon reaching 10th level, there's a 48% chance that a fractional ability score has gone up by a point.
- Upon reaching 11th level, there's a 79% chance that a fractional ability score has gone up by a point.
- Upon reaching 12th level, there's a 94% chance that a fractional ability score has gone up by a point.
To throw another wrench into the plan, I ruled that when you use the +1/4 levels ability increase, it resets that ability's fractional score to zero. My thinking was that I didn't want the player's to stack the "once every four levels" bonus with the fractional bonus and potentially increase a score twice upon gaining a level.
The campaign is limited to 20 levels and we most likely won't even reach that. This fractional ability score thing seems like a lot of extra accounting with very little payoff.How do I tell the players "This house rule sucks and we shouldn't do it anymore?" I don't want them to feel like they are missing out, but at the same time I don't want them to be doing a bunch of extra paperwork and accounting for no reason.