Let $$X$$ be a normal random variable with mean $$1$$ and variance $$4.$$ The probability $$P\left\{ {X < 0} \right\}$$ is

A box contains $$2$$ washers, $$3$$ nuts and $$4$$ bolts. Items are drawn from the box at random one at a time without replacement. The probability of drawing $$2$$ washers first followed by $$3$$ nuts and subsequently the $$4$$ bolts is

The standard deviation of a uniformly distributed random variable $$b/w$$ $$0$$ and $$1$$ is

If three coins are tossed simultaneously, the probability of getting at least one head is