Question

What is standard deviation of tossing a biased coin?

Answer 1

Answer:

When tossed, a biased coin yields heads with probability 20% and tails with probability 80%. Let X denote the number of heads obtained when the coin is tossed 36 times.

Answer 2

Answer:

Step-by-step explanation:When tossed, a biased coin yields heads with probability 20% and tails with probability 80%. Let X denote the number of heads obtained when the coin is tossed 36 times. Find the standard deviation of X.

So I think I found the pdf to be (36 choose x)(.2)^x(.8)^x; but I'm not sure.

Standard deviation I know is (var(x))^(1/2) and var(x)=E(x^2)-(E(x))^(1/2). Knowing this, I'm not sure what to do next...