Find the variance of the distribution:

A random variable X has the distribution. Then , variance of the distribution, is

An urn contains 3 white and 6 red balls. 4 balls are drawn one by one with replacement from the urn.Find the probability distribution of the number of red balls drawn. Also find mean and variance of the distribution.

Three numbers are selected at random (without replacement) from first 6 positive integers. Let X denote the largest of the three numbers obtained. Find the probability distribution of X. Also, find the mean and variance of the distribution.

Find the probability distribution of the number of white balls drawn in a random draw of 3 balls without replacement from a bag containing 4 white and 6 red balls. Also find the mean and variance of the distribution.

Two dice are rolled at random 5 times. Obtain the mean and variance of the distribution of doublets obtained.

If 12 dice are rolled at random, obtain the mean and variance of the distribution of successes, if 'getting a number greater than 4' is considered a success.

Two numbers are selected at random from first six positive integers. Let X denote the larger of the two numbers obtained. Find the probability distribution of X. find the mean and variance of this distribution.

The screws produced by a certain machine were checked by examining samples of 7. The following table shows the distribution of 128 samples according to the number of defective items they contained. Fit a binomial distribution and find the expected frequencies if the chance of screw being defective is 1/2 . Also find the mean and variance of the fitted distribution.

Find the variance of the number obtained on a throw of an unbiased die.

The variance of 20 observations is 5. If each observation is multiplied by 2, find the new variance of the resulting observations.