The probability that an event A happens in one treat of an experiment is 0.4. Three independent treats of the experiment are performed. Find the p!probability that the event A happens at least once.

The standard deviation of a binomial distribution (q +p)¹⁶ is 2. Find its mean.

If a random variable X follows Poisson distribution such that P(X = 2) = 9. P(X = 4) + 90 P(X = 6) then find the mean and variance.

Find the value of K if X is a normal variate whose p.d.f is given by f(x)  = \(\frac { 1 }{ K } \)e^8x-4x2, -∞

Obtain K, μ and σ2 of of the normal distribution whose probability distribution function is f(x) = \(K{ e }^{ -2x^{ 2 }+4x-2 }\), -∞