Question

Let X be the number of Heads in 10 fair coin tosses. (a) Find the conditional PMF of X, given that the first two tosses both land Heads. (b) Find the conditional PMF of X, given that at least two tosses land Heads

Answer 1

Answer:

Follows are the solution to the given point:

Step-by-step explanation:

For option A:

In the first point let z be the number of heads which is available on the first two trails of tosses so, the equation is:

$P(X=k | z=2 ) = \begin{pmatrix} 10-2\\ k-2\end{pmatrix} (\frac{1}{2})^{k-2} (\frac{1}{2})^{10-k}$

                         $= \begin{pmatrix} 8\\k-2\end{pmatrix} (\frac{1}{2})^{k-2} (\frac{1}{2})^{10-k}$

                                                                                                       $k= 2,3..........10$For option B:

$P(X=k | X \geq 2 ) = \sum^{10}_{i=2} \begin{pmatrix} 10-i\\ k-i\end{pmatrix} (\frac{1}{2})^{k-i} (\frac{1}{2})^{10-k}$

                                                                                                $k= 2,3, 4.........10$