Suppose that you throw 2 dice 20 times. Find the probability that you get at least one (1, 1) is:-
I thought like this,
let X=Number of (1,1) we get in 20 throws. SO X represents a Binomial random variable
B($20$,$1/36$). So we have to find out P(X=1)+P(X=2).
Is this approach right?
Is this a binomial RV?
0
$\begingroup$
probability
probability-distributions
1 Answers
1
Everything is okay up to "So..."
You indeed have a binomial random variable.
$$X \sim\mathcal{Bin}(20,1/36)$$
The probability for getting at least one $(1,1)$ in twenty throws, is the probability for not getting none. IE: Use complements.
$$\mathsf P(X\geq 1)~~=~~ 1-\mathsf P(X=0)$$