Hello,

Tiny typo that doesn't affect the result

(it's actually binomial, since there are successive Bernoulli events)

I don't really know how you got your formula, but your friend's is correct :b) I am a little confused as to which equation I should be using for this. My professor gave us the Binomial Theorem, Geometric Prob Law, and the Multinomial Prob Law. I am a bit unsure as to which case this is. Here is what I did using the Binomial Prob Law:

n=5; k=2

10p^k(1-p)^(n-k)

(10)(0.3)^2 (0.7)^3 = 0.3087

I have a friend who did something like this but I am unsure if this is correct either:

1 - (0.7)^6 - 6*.3*(.7)^5

, and that's because X takes values into {0,1,2,3,4,5,6}. So if X<2, then it's equal to 0 or 1.

Looks correct to mec) p^1 (1-p)^5

0.3(1-0.3)^5 * (6!/5!)

(6)(0.3)(0.7)^5 = 0.302526

Since we are only interested in finding the possibility for the last one, we would divide by 6 since the previous line is for w/o ordering.

0.302526/6 = 0.050421