Rolling Probability

[edk926]

I have a couple of questions for those that remember statistics.

1) If you give a character 4 disadvantages with the default '12 or less' for success, and roll on each once per day, what's the probability to succeed all 4 rolls?

2) Say you just start rolling many times. What would be the average number of rolls before you roll a 16 or greater?

[whswhs]

Originally Posted by edk926

I have a couple of questions for those that remember statistics.

1) If you give a character 4 disadvantages with the default '12 or less' for success, and roll on each once per day, what's the probability to succeed all 4 rolls?

2) Say you just start rolling many times. What would be the average number of rolls before you roll a 16 or greater?

1) The chance of rolling a 12 or less is 160/216, or 0.74074. The chance of doing so four times is the fourth power of that, or 0.30107. So on the average you'll make the roll every 3 1/3 days.

2) The chance of rolling a 16 or better is 10/216, or 0.04630. The expected number of rolls to do so is the inverse of that number, or 216/10, or 21.6.