A+ Answers

Question 1.1. Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers. Accordingly, his staff recorded the waiting times for 45 randomly selected walk-in customers, and calculated that their mean waiting time was 15 minutes. If Brian concludes that the average waiting time for all walk-in customers is 15 minutes, he is using a/an ________. (Points : 3)

       range estimate
       statistical parameter
       interval estimate
       point estimate
       exact estimate

Question 2.2. Brian Vanecek, VP of Operations at Portland Trust Bank, is evaluating the service level provided to walk-in customers. Accordingly, his staff recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 14 minutes. Assume that the population standard deviation is 4 minutes. The 90% confidence interval for the population mean of waiting times is ________. (Points : 3)

       14.27 to 15.73
       14.18 to 15.82
       9.88 to 20.12
       13.18 to 14.82
       18.12 to 19.87

Question 3.3. The normal distribution is used to test about a population mean for large samples if the population standard deviation is known. "Large" is usually defined as _______. (Points : 3)

       at least 10
       at least 5% of the population size
       at least 30
       at least 12
       at least 100

Question 4.4. Consider the following null and alternative hypotheses.
                                    Ho: p < 0.16
                                    Ha: p > 0.16
These hypotheses _______________. (Points : 3)

       indicate a one-tailed test with a rejection area in the right tail
       indicate a one-tailed test with a rejection area in the left tail
       indicate a two-tailed test
       are established incorrectly
       are not mutually exclusive

Question 5.5. A company produces an item that is supposed to have a 6-inch hole punched in the center. A quality control inspector is concerned that the machine that punches the hole is "out of control" (hole is too large or too small). In an effort to test this, the inspector is going to gather a sample punched by the machine and measure the diameter of the hole. The alternative hypothesis used to statistically test to determine if the machine is out of control is (Points : 3)

       the mean diameter is > 6 inches
       the mean diameter is < 6 inches
       the mean diameter is = 6 inches
       the mean diameter is ≠ 6 inches
       the mean diameter is ≥ 6 inches

Question 6.6. A researcher is testing a hypothesis of a single mean. The critical z value for a = .05 and a two‑tailed test is +1.96. The observed z value from sample data is ‑2.05. The decision made by the researcher based on this information is to _____ the null hypothesis. (Points : 3)

       reject
       not reject
       redefine
       change the alternate hypothesis into
       restate the null hypothesis

Question 7.7. Jennifer Cantu, VP of Customer Services at Tri-State Auto Insurance, Inc., monitors the claims processing time of the claims division. Her standard includes "a mean processing time of 5 days or less." Each week, her staff checks for compliance by analyzing a random sample of 60 claims. Jennifer's null hypothesis is ________. (Points : 3)

       m > 5
       s > 5
       n = 60
       m < 5
       m = 5

Question 8.8. Restaurateur Denny Valentine is evaluating two sites, Raymondville and Rosenberg, for his next restaurant. He wants to prove that Raymondville residents (population 1) dine out more often than Rosenberg residents (population 2). Denny plans to test this hypothesis using a random sample of 81 families from each suburb. His null hypothesis is __________. (Points : 3)

       s₁² < s₂²
       mm₁ - mm₂ ³ 0
       p₁ – p₂ = 0
       m₁ - m₂ = 0
       s₁ – s₂ = 0

Question 9.9. Lucy Baker is analyzing demographic characteristics of two television programs, COPS (population 1) and 60 Minutes (population 2). Previous studies indicate no difference in the ages of the two audiences. (The mean age of each audience is the same.) Lucy plans to test this hypothesis using a random sample of 100 from each audience. Her alternate hypothesis is ____________. (Points : 3)

       m₁ - m₂ < 0
       m₁ - m₂  ³ 0
       m₁ - m₂ = 0
       m₁ - m₂ ¹ 0
       m₁ - m₂ = 1

Question 10.10. Maureen McIlvoy, owner and CEO of a mail order business for wind surfing equipment and supplies, is reviewing the order filling operations at her warehouses. Her goal is 100% of orders shipped within 24 hours. In previous years, neither warehouse has achieved the goal, but the East Coast Warehouse has consistently out-performed the West Coast Warehouse. Her staff randomly selected 200 orders from the West Coast Warehouse (population 1) and 400 orders from the East Coast Warehouse (population 2), and reports that 190 of the West Coast Orders were shipped within 24 hours, and the East Coast Warehouse shipped 372 orders within 24 hours. Maureen's null hypothesis is ____. (Points : 3)

       p₁ – p₂ = 0
       m₁ - m₂ = 0
       p₁ – p₂ > 0
       m₁ - m₂ < 0
       m₁ - m₂ ≥ 0