Suppose a manager has two potential suppliers of a part, A and B.  The following lists show the number of defective parts that have been found in a shipment of 1000 parts for a large number of shipments over the years.  Let XA = number of defective parts for supplier A.  XB is a similar count for supplier B.

1. Find E(XA) and E(XB).

2. If the manager has to choose one supplier, which should he choose to minimize the number of defects over time?  Explain.
 
 
 
 

XA	P(XA)	.
0	0.95	.
1	0.035	.
10	0.01	.
20	0.005	.

 

XB	P(XB)	.
0	0.93	.
1	0.06	.
2	0.006	.
10	0.003	.
25	0.001	.