Business and Management IKEA is a Swedish company that sells ready-to-assemble furniture. Shoppers contact customer service with regard to finding a nearby store, online shipping questions, and even for help with assembly. IKEA classifies all telephone calls to its customer support staff by the amount of time the customer is on hold. If the customer is on hold for no more than 60 seconds, then the call is classified as successful (actually, this sounds like a miracle). The supervisor in technical support claims 80% of all calls are successful. Suppose 25 calls to technical support are selected at random.
a. Find the mean, variance, and standard deviation of the number of successful calls.
b. Find the probability that at least 18 calls will be successful.
c. Suppose 21 calls are successful. Is there any evidence to suggest the supervisor's claim is false? Justify your answer.