you wouldn't want to be obvious, if you get 30+ random(70) that is very obvious
how about simple:
Round(100.0 * Exp(Ln(RandomE + 0.0001) * 0.9)))
it gives you numbers from 0 to 100 with mid range of random giving you 54 slightly curved up faster, undetectable unless you get way too many samples, and slightly higher chance of higher number
edit: of course the +0.0001 offset is only needed only because you really wouldn't want to get RandomE to return 0, because Ln(0) is undefined
basically it is: Y = 100 * (x^0.9), so 0 maps to 0, 1 maps to 100 and it always goes a little bit higher than straight line