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ITIS 1P97: Data Analysis and Business Modeling

Lab Exercise 4: Descriptive Statistics and Probability

Problems and exercises (Chapters 4 and 5 of the textbook). The data files required for the exercises are available on Sakai for download.

1.  (Problem 4.2) In the Excel file Facebook Survey, find the average and median hours online/week and number of friends in the sample using the appropriate Excel functions. Compute the midrange and compare all measures of location.

Use descriptive statistics (Data Analysis Toolpack) to find out descriptive statistics of this dataset.

2.  (InClass Example) Suppose that we are interested in the number of arrivals at the drive-up teller window of a bank during a 15-minute period on weekday mornings.

An analysis of historical data shows that the average number of cars arriving during a 15-minute interval of time is 10. The Poisson probability function with l = 10 applies. What is the probability of five arrivals in 15 minutes.

3. (InClass Example) A Brock Club cafeteria sells a popular on-tap drink.  When the stock of this drink drops to 20 gallons, a replenishment order is placed.

The store manager is concerned that sales are being lost due to stock-outs while waiting for an order.  It has been determined that demand during replenishment lead-time is normally distributed with a mean of 15 gallons and a standard deviation of 6 gallons.

The manager would like to know the probability of a stockout, P(x > 20).

Additional Practice problems

4. (Problem 5.16) Using the data in the Excel file Consumer Transportation Survey, develop a contingency table for Gender and Vehicle Driven; then convert this table into probabilities.

a. What is the probability that respondent is female?

b. What is the probability that a respondent drives an SUV?

c. What is the probability that a respondent is male and drives a minivan?

d. What is the probability that a female respondent drives either a truck or an SUV?

e. If it is known that an individual drives a car, what is the probability that the individual is female?

f. If it is known that an individual is male, what is the probability that he drives an SUV?

g. Determine whether the random variables “gender” and the event “vehicle driven” are statistically independent. What would this mean for advertisers?

5. (Problem 5.42) The actual delivery time from Giodanni’s Pizza is exponentially distributed with a mean of 20 minutes.

h. What is the probability that the delivery time will exceed 30 minutes?

i. What proportion of deliveries will be completed within 20 minutes?