a midwestern company that produces widgets organized its workers in four groups in order to compare the productivity of four different manufacturing protocols. the mean productivity of each protocol is given below. using the weighted average calculate the overall mean productivity for the four different protocols.

Protocol 1 X = 20, N = 10

Protocol 2 X = 15, N = 14

Protocol 3 X = 18, N = 15

Protocol 4 X =22, N = 8