Find the mean , variance and standard deviation :

Calculate the mean, variance and standard deviation for the following distribution :

Calcuate the mean, variance and standard deviation of number of heads in two tosses of a coin.

A class has 15 students whose ages are 14, 17, 15, 14, 21, 17, 19, 20, 16, 18, 20, 17, 16, 19 and 20 years. One student is selected in such a manner that each has the same chance of being chosen and the age X of the selected student is recorded. What is the probability distribution of the random variable X? Find mean, variance and standard deviation of X.

Calcuate the mean variance and standard deviation of a number obtained as a result of throwing. an unbiased die.

Find the variance and standard deviation for the following data :

Let X denote the sum of the numbers obtained when two fair dice are rolled. Find the variance and standard deviation of X.