# Thread: Average number, determine probability

1. ## Average number, determine probability

" Suppose the average number of cars abandoned weekly on a certain highway is 2.2. Approximate
i) no abandoned cars in next week
ii) at least 2 abandoned in the next week
"

From the question we know that if X denotes the number of abandoned cars on the road then E(X)=2.2 and that since this is discrete:
$\displaystyle E(X)=\sum_{i=0}^{\infty}x_iP(X=x_i)=2.2$

and we want to find
$\displaystyle P(X=0), P(X \geq 2)=1-P(X<2)$
But we dont know what type of distribution this is...any help would be appreciated.

2. Originally Posted by Pur
" Suppose the average number of cars abandoned weekly on a certain highway is 2.2. Approximate
i) no abandoned cars in next week
ii) at least 2 abandoned in the next week
"

From the question we know that if X denotes the number of abandoned cars on the road then E(X)=2.2 and that since this is discrete:
$\displaystyle E(X)=\sum_{i=0}^{\infty}x_iP(X=x_i)=2.2$

and we want to find
$\displaystyle P(X=0), P(X \geq 2)=1-P(X<2)$
But we dont know what type of distribution this is...any help would be appreciated.
Perhaps you're meant to assume a Poisson distribution ....?