12.7. At one time 200ohm resistors, made to 0.75%, that is, to 200 1.5 ohms...

12.7. At one time 200ohm resistors, made to ¼ 0.75%, that is, to 200  1.5 ohms were quite costly, due in part to the necessity of sorting out those outside the limits. But production was able to manufacture 100ohm resistors to 1% without sorting and with good normality of distribution. Take m

¼100, s¼0.33 ohm. Now assembling at random two 100ohm resistors in series gives what distribution for total resistance? Will such a distribution meet limits of 2001.5 ohms? Take note that we should check on the independence of resistances in 100ohm resistors, because wire diameter might cause nonindependence. (A company made quite large savings using this approach.)