Question

Let the random variable x be equally likely to assume any of the values 1/10, 1/5, or 3/10. determine the mean and variance of x. the mean is

Answer 1

Since the values are equally likely and equally spaced, their mean is the middle one.
  the mean is 1/5

The variance is the average of the square of the deviations from the mean.
  σ² = (1/3)((-1/10)² + 0² + (1/10)²) = 2/300
  the variance is 2/300