After the last few threads I've seen on this subject were tantamount to a mathematical abortion, I decided to end all this nonsense and just make a calculator. Here it is:

Scrolling Probability Calculator

http://glue.umd.edu/~mdevries/scroll.html


Currently, only 10% and 60% are counted. 100% is trivial of course, but if we get 30% and 70%, they will be trivially easy for me to add. ANY combination is possible. Simply choose whether you want to find exactly X out of Y scrolls, or at least X out of Y scrolls for both 10% and 60%, then click solve, and you're done.

I tried to make my nCr and factorial functions as efficient as possible, however factorials will do as factorials do, so of course large scroll numbers (>100) may take some time to calculate.


Here is an example: I want to make a +3 (10%) or better Blue Crusader Chainmail. I will be discarding blue crusader chainmails that fail on the first try, but I want to know about how many scrolls it will take so that I have a 50% chance of any one of those scrolls working, giving me a +1 9slot chainmail. I put in Exactly 0 out of 0 60%, and At Least 1 out of (I'll guess, 10) 10%. This gives 65.132%, but I want 50%, so I decrement the total 10% scrolls until I get closer. At least 1 out of 7 scrolls gives 52.17%. This means that the chance of me getting my +1 9 slot crusader is about the same as winning a coin toss when I use 7 scrolls.

Now I want my chainmail to be +3. It is +1 with 9 slots, so I have 9 scrolls left, and I want At least 2 to work, so I enter At least 2 out of 9 10% scrolls and hit Solve. The probability of me getting my +3 on this chainmail is 22.516%.



In all honesty, this really has little bearing on the game. You scroll what you scroll, but it is sometimes nice to see just how lucky (or unlucky) you got. After seeing a post about this pop up once a week though, it was time to close the discussion.


Enjoy.