Random Variables- Properties of Variance/Standard Deviation

A mason is contracted to build a patio retaining wall. Plans call for the base of the wall to be a row of 50 10-inch bricks, each separated by ½ inch thick mortar. Suppose that the bricks used are randomly chosen from a population of bricks whose meanlength is 10 inches and whose standard deviationis 1/32 inch. Also suppose that the mason, on the average, will make the mortar ½ inch thick, but the actual dimension varies from brick to brick, the standard deviation of the thickness being 1/16 inch. What is the standard deviation of L, the length of the first row of the wall?

We know that if the length of bricks and thickness of mortar are all independent random variables, we have the following …

Properties of variances and standard deviations are examined.