A fair coin is tossed four times. What is the probability that at most three tails occur ?

Two students X and Y appeared in an examination. The probability that X will qualify…

The variance of 20 observations is 5. If each observation is multiplied by 2, then…

What is the mean deviation about the mean for the data 4, 7, 8, 9,…

If x̄ and ȳ are the means of two distributions such that x̄ < ȳ…

There are 4 white and 3 black balls in a box. In another box, there…