Originally Posted by

**Jhevon** ok, so we are using the binomial distribution, for which the formula is, i'm sure you're familiar with what the variables mean, so i won't define them, $\displaystyle P(X = k) \mbox{ or } P(k) = {n \choose k}p^kq^{n - k}$

so for this set of questions, n = 25 always.

for (a), you want $\displaystyle P(X \ge 2) = 1 - P(0) - P(1)$, here we have p = 2/38. you got that i think. hope your calculations are correct

for (b) you're not correct. here we want $\displaystyle P(0)$, p = 2/38 also here.

for (c) you want $\displaystyle P(X \ge 15) = P(15) + P(16) + P(17) + ... + P(25)$. here p = 18/38

for (d) you want $\displaystyle P(X \le 10) = P(0) + P(1) + P(2) + ... + P(10)$. here p = 18/38