Many of a bank’s customers use its automatic teller machine to transact business after normal banking hours. During the early evening hours in the summer months, customers arrive at a certain location at the rate of one every other minute. This can be modeled using a Poisson distribution. Each customer spends an average of 100 seconds completing his or her transactions. Transaction time is exponentially distributed. a. Determine the average time customers spend at the machine, including waiting in line and completing transactions. (Do not round intermediate calculations. Round your answer to the nearest whole number.) Average time _____ minutes b. Determine the probability that a customer will not have to wait upon arriving at the automatic teller machine. (Round your answer to 2 decimal places.) Probability _____ c. Determine the average number of customers waiting to use the machine. (Round your answer to 2 decimal places.)
Continuous Probability Distributions
Probability distributions are of two types, which are continuous probability distributions and discrete probability distributions. A continuous probability distribution contains an infinite number of values. For example, if time is infinite: you could count from 0 to a trillion seconds, billion seconds, so on indefinitely. A discrete probability distribution consists of only a countable set of possible values.
Normal Distribution
Suppose we had to design a bathroom weighing scale, how would we decide what should be the range of the weighing machine? Would we take the highest recorded human weight in history and use that as the upper limit for our weighing scale? This may not be a great idea as the sensitivity of the scale would get reduced if the range is too large. At the same time, if we keep the upper limit too low, it may not be usable for a large percentage of the population!
a. Determine the average time customers spend at the machine, including waiting in line and completing transactions. (Do not round intermediate calculations. Round your answer to the nearest whole number.)
Average time _____ minutes
b. Determine the
Probability _____
c. Determine the average number of customers waiting to use the machine. (Round your answer to 2 decimal places.)
Average number ______ customers
Given Information:
Customers arrive at bank's ATM at the rate of 30 per hour. (one every other minute)
The average time the customer spends completing his or her transactions is 100 seconds.
The arrival rate is per hour.
Average service rate is calculated as shown below:
This implies:
(a) To determine the average time customers spend at the machine, including waiting in line and completing transactions:
Waiting time:
Thus, the average time customers spend at the machine, including waiting in line and completing transactions is 10 minutes.
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