Response times for telephone repair calls. A study

Chapter , Problem 15.47

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Response times for telephone repair calls. A study examined the time required for the telephone company Verizon to respond to repair calls from its own customers and from customers of a CLEC, another phone company that pays Verizon to use its local lines. Here are the data, which are rounded to the nearest hour: TREPAIR Verizon 111 1 2 2 1 1 1 1 2 2 111 1 2 2 1 1 1 1 2 3 111 1 2 3 1 1 1 1 2 3 111 1 2 3 1 1 1 1 2 3 111 1 2 3 1 1 1 1 2 4 111 1 2 5 1 1 1 1 2 5 111 1 2 6 1 1 1 1 2 8 1 1 1 1 2 15 1 1 1 2 2 CLEC 115 5 5 1 5 5 5 5 (a) Does Verizon appear to give CLEC customers the same level of service as its own customers? Compare the data using graphs and descriptive measures and express your opinion. (b) We would like to see if times are significantly longer for CLEC customers than for Verizon customers. Why would you hesitate to use a t test for this purpose? Carry out a rank test. What can you conclude? (c) Explain why a nonparametric procedure is appropriate in this setting. Iron-deficiency anemia is the most common form of malnutrition in developing countries. Does the type of cooking pot affect the iron content of food? We have data from a study in Ethiopia that measured the iron content (milligrams per 100 grams of food) for three types of food cooked in each of three types of pots:19 COOK Type of Pot Iron Content Meat Aluminum 1.77 2.36 1.96 2.14 Clay 2.27 1.28 2.48 2.68 Iron 5.27 5.17 4.06 4.22 Legumes Aluminum 2.40 2.17 2.41 2.34 Clay 2.41 2.43 2.57 2.48 Iron 3.69 3.43 3.84 3.72 Vegetables Aluminum 1.03 1.53 1.07 1.30 Clay 1.55 0.79 1.68 1.82 Iron 2.45 2.99 2.80 2.92