Discussion:
Q1: The Commercial Bank and Trust Company is studying the use of its automatic teller machines (ATMs). Of particular interest is whether young adults (under 25 years) use the machines more than senior citizens. To investigate further, samples of customers under 25 years of age and customers over 60 years of age were selected. The number of ATM transactions last month was determined for each selected individual, and the results are shown below. At the .01 significance level, can bank management conclude that younger customers use the ATMs more?
Under 25 10 10 11 15 7 11 10 9
Over 60 4 8 7 7 4 5 1 7 4 10 5
Q2: An investigation of the effectiveness of an antibacterial soap in reducing operating room contamination resulted in the accompanying table. The new soap was tested in a sample of eight operating rooms in the greater Seattle area during the last year.
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Operating Room
A B C D E F G H
Before 6.6 6.5 9.0 10.3 11.2 8.1 6.3 11.6
After 6.8 2.4 7.4 8.5 8.1 6.1 3.4 2.0
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At the 0.05 significance level, can we conclude the contamination measurements are lower after use of the new soap?
Q3: The city of Laguna Beach operates two public parking lots. The one on Ocean Drive can accommodate up to 125 cars and the one on Rio Rancho can accommodate up to 130 cars. City planners are considering both increasing the size of the lots and changing the fee structure. To begin, the Planning Office would like some information on the number of cars in the lots at various times of the day. A junior planner officer is assigned the task of visiting the two lots at random times of the day and evening and counting the number of cars in the lots. The study lasted over a period of one month. Below is the number of cars in the lots for 25 visits of the Ocean Drive lot and 28 visits of the Rio Rancho lot.
Ocean
89 115 93 79 113 77 51 75 118 105 106 91 54
63 121 53 81 15 67 53 69 95 121 88 64
Rio Rancho
128 110 81 126 82 114 93 40 94 45 84 71 74
92 66 69 100 114 113 107 62 77 80 107 90 129
105 124
Is it reasonable to conclude that there is a difference in the mean number of cars in the two lots? Use the .05 significance level.