Return to the information for tile width and tile length given in Example 11.4. (a) Give the expected difference in tile widths and length, D = width - length. (b) Give the variance for D and the...

Return to the information for tile width and tile length given in Example 11.4.

(a) Give the expected difference in tile widths and length, D = width - length.

(b) Give the variance for D and the standard deviation.

 Example 11.4

The width of a tile has a mean of 12 inches and a variance of 0.0025 inches². The length has a mean of 12 inches and a variance of .0064 inches2. Tiles that are wider than usual tend to be longer than usual, as reflected in a covariance of 0.0026. What is the variance of T = width + length?