Suppose you purchase 50,000 electrical switches and the supplier guarantees that the shipment will contain no more than 0.1% defectives. To check the shipment, you randomly sample 500 switches, test them, and find that 4 are defective. Assuming the supplier’s claim is true, compute the mean and the standard deviation for the number of defectives in a sample of 500 switches. If the supplier’s claim is true, is it likely that you have found 4 defective switches in the sample? Based on this sample, what inference would you make concerning the supplier’s guarantee?