A random variable X has the following probability distribution
|
X |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
|
P(X = x) |
0 |
k |
2k |
2k |
3k |
k2 |
2k2 |
7k2 + k |
Then value of P for $(0 < X < 5)$
Answer & explanation
Correct answer: option 3
P(X) = 1
∴ P(0) + P(1) + P(2) + P(3) + P(4) + P(5) + P(6) + P(7) = 1
∴ 0 + k + 2k + 2k + 3k + k2 + 2k2 + 7k2 + k = 1
9k + 10k2 - 1 = 0
10k2 + 9k - 1 = 0 ⇒ 10k2 + 10k - k - 1 = 0
10k (k + 1) - 1(k + 1) = 0 ⇒ (k + 1)(10k - 1) = 0
∴ k +1 = 0
k = -1
k ≠ -1
∴ 10k - 1 = 0
$k = \frac{1}{10}$ ...(i)
Value of P(0 < x < 5) = 0 + k + 2k + 2k + 3k
$8k = 8×\frac{1}{10}=\frac{8}{10}=\frac{4}{5}$
Option 3 is correct.