A supplier to a car manufacturer produces a certain valve and seal used in their cars. The sizes of these seals and valves are closely monitored to ensure the parts actually work. Here are summary statistics on the diameters for
these valves and seals (in millimeters).
Mean
Standard deviation
Valve
Hv = 50
OV = 0.3
Seal
Ils = 51
Os = 0.4
Both distributions are approximately normal. A seal properly fits a valve if the seal's diameter is larger than the
valve's diameter, but the difference can't be more than 2 mm. Suppose we choose a valve and seal at random
and calculate the difference between their diameters. We can assume that their diameters are independent.