The sum and product of the mean and variance of a binomial distribution are 82.5 and 1350 respectively. Then the number of trials in the binomial distribution is ____________.
A bag contains 4 white and 6 black balls. Three balls are drawn at random from the bag. Let $$\mathrm{X}$$ be the number of white balls, among the drawn balls. If $$\sigma^{2}$$ is the variance of $$\mathrm{X}$$, then $$100 \sigma^{2}$$ is equal to ________.
The probability distribution of X is :
X | 0 | 1 | 2 | 3 |
---|---|---|---|---|
P(X) | $${{1 - d} \over 4}$$ | $${{1 + 2d} \over 4}$$ | $${{1 - 4d} \over 4}$$ | $${{1 + 3d} \over 4}$$ |
For the minimum possible value of d, sixty times the mean of X is equal to _______________.
Let S = {E1, E2, ........., E8} be a sample space of a random experiment such that $$P({E_n}) = {n \over {36}}$$ for every n = 1, 2, ........, 8. Then the number of elements in the set $$\left\{ {A \subseteq S:P(A) \ge {4 \over 5}} \right\}$$ is ___________.