(a) To find the probability that Sadie takes exactly 1 red ball, we calculate the probability of choosing 1 red ball and 2 blue balls. The probability is given by:
\(P(1 \text{ red}) = \frac{5}{8} \times \frac{3}{7} \times \frac{2}{6} = \frac{15}{56}\)
(b) The probability distribution table for X is:
| x | 0 | 1 | 2 | 3 |
|---|
| Prob. | \(\frac{1}{56}\) | \(\frac{15}{56}\) | \(\frac{30}{56}\) | \(\frac{10}{56}\) |
(c) To find \(\text{Var}(X)\), we use the formula:
\(\text{Var}(X) = E(X^2) - (E(X))^2\)
First, calculate \(E(X^2)\):
\(E(X^2) = 0^2 \times \frac{1}{56} + 1^2 \times \frac{15}{56} + 2^2 \times \frac{30}{56} + 3^2 \times \frac{10}{56}\)
\(E(X^2) = \frac{15}{56} + \frac{120}{56} + \frac{90}{56} = \frac{225}{56}\)
Now, substitute into the variance formula:
\(\text{Var}(X) = \frac{225}{56} - \left( \frac{15}{8} \right)^2\)
\(\text{Var}(X) = \frac{225}{56} - \frac{225}{64}\)
\(\text{Var}(X) = 0.502\)