1. Trading volume on the New York Stock Exchange is heaviest during the first half hour (early morning) and last half hour (late afternoon) of the trading day. The early morning trading volumes (millions of shares) for 13 days in January and February are shown here (Barron's, January 23, 2006; February 13, 2006; and February 27, 2006).

214	163	265	194	180
202	198	212	201
174	171	211	211

The probability distribution of trading volume is approximately normal.

1. Compute the mean and standard deviation to use as estimates of the population mean and standard deviation.
2. What is the probability that, on a randomly selected day, the early morning trading volume will be less than 180 million shares?

What is the probability that, on a randomly selected day, the early morning trading volume will exceed 230 million shares?

2. When a customer places an order with Rudy's On-Line Office Supplies, a computerized accounting information system (AIS) automatically checks to see if the customer has exceeded his or her credit limit. Past records indicate that the probability of customers exceeding their credit limit is 0.05. Suppose that, on a given day, 20 customers place orders. Assume that the number of customers that the AIS detects are having exceeded their credit limit is distributed as a binomial random variable.

a. What are the mean and standard deviation of the number of customers exceeding their credit limits?

b. What is the probability that 0 customers will exceed their limits?