# Math Help - Binomial probability P(X<2)

1. ## Binomial probability P(X<2)

Hi,

Calculating the probability as stated below, I cannot make it work because by my calculations it is undefined where n=8 and x=0

p=0.20
n = 8
x < 2

P(x <2)= P(x=0)+P(x=1)
= 8/0*(0.20)^0*(1-0.20)^8 + 8/1*(0.20)^1*(1-0.20)^7

What is wrong with my workings?

Thanks
Splint

Update: Would it be more appropriate to write it as 1-(P((X=2)+(X=3)+(X=4)+(X=5)+(X=6)+(X=7)+(X=8))

2. ## Re: Binomial probability P(X<2)

The part $\binom{n}{k}$ in the formula for the binomial distribution is a binomial coefficient and not the ratio $\frac{n}{k}$.