if you are 85% accurate most of the time, what is the probabilty you will be correct 4 times in a row?

Question

So I figure for 3 out of 5, you do 3/5 = .60, and then take that and do .60/.085, which would give you 70%. But how do I find the probabilty of being accurate extactly 4 tines in the next days? Thanks...

Answer 1

(0.85)^4 = 0.52X100% = ~52%

Answer 2

It's simply .85^4.

Whatever you were thinking of with the 3/5, you were confused.

If you were looking for the probability of being right N times out of M days, with M>N, you'd be looking at a polynomial in .85 or, equivalently, a polynomial in .85 and .15 (since .15 = 1-.85 - the probability of being WRONG).

The site I'm linking below is a lot of fun for problems like this.