There is noting to calculate for bias in 15 rolls, dumb to even mention it! Any calculation to determine if there is a chance that a bias exists is answered in terms of percentage of confidence. There is no way a 15 roll data base provides any reliable percentage of confidence of a bias...none! You are the newest member of the elite innumerate club......not to mention a very delusional individual. But maybe not really, maybe just our newest resident troll.