More on interpreting the s chart. Each of the 4

Chapter , Problem 17.71

(choose chapter or problem)

More on interpreting the s chart. Each of the 4 out-of-control values of s in part (a) of the previous exercise is explained by a single outlier, a very long response time to one call in the sample. You can see these outliers in Figure 17.17(b). What are the values of these outliers, and what are the s-values for the 4 samples when the outliers are omitted? (The interpretation of the data is, unfortunately, now clear. Few customers will wait 5 minutes for a call to be answered, as the customer whose call took 333 seconds to answer did. We suspect that other customers hung up before their calls were answered. If so, response time data for the calls that were answered dont adequately picture the quality of service. We should now look at data on calls lost before being answered to see a fuller picture.) 17.3 Process Capability Indexes 17-51 Sample Time (seconds) Sample mean Standard deviation 1 59 13 2 24 11 18 21.2 19.93 2 38 12 46 17 77 12 33.7 25.56 3 46 44 4 74 41 22 38.5 23.73 4 25 7 10 46 78 14 30.0 27.46 5 6 9 122 8 16 15 29.3 45.57 6 17 17 9 15 24 70 25.3 22.40 7 9 9 10 32 9 68 22.8 23.93 8 8 10 41 13 17 50 23.2 17.79 9 12 82 97 33 76 56 59.3 32.11 10 42 19 14 21 12 44 25.3 14.08 11 63 5 21 11 47 8 25.8 23.77 12 12 4 111 37 12 24 33.3 39.76 13 43 37 27 65 32 3 34.5 20.32 14 9 26 5 10 30 27 17.8 10.98 15 21 14 19 44 49 10 26.2 16.29 16 24 11 10 22 43 70 30.0 22.93 17 27 10 32 96 11 29 34.2 31.71 18 7 28 22 17 9 24 17.8 8.42 19 15 14 34 5 38 29 22.5 13.03 20 16 65 6 5 58 17 27.8 26.63 21 7 44 14 16 4 46 21.8 18.49 22 32 52 75 11 11 17 33.0 25.88 23 31 8 36 25 14 85 33.2 27.45 24 4 46 23 58 5 54 31.7 24.29 25 28 6 46 4 28 11 20.5 16.34 26 111 6 3 83 27 6 39.3 46.34 27 83 27 2 56 26 21 35.8 28.88 28 276 14 30 8 7 12 57.8 107.20 29 4 29 21 23 4 14 15.8 10.34 30 23 22 19 66 51 60 40.2 21.22 31 14 111 20 7 7 87 41.0 45.82 32 22 11 53 20 14 41 26.8 16.56 33 30 7 10 11 9 9 12.7 8.59 34 101 55 18 20 77 14 47.5 36.16 35 13 11 22 15 2 14 12.8 6.49 36 20 83 25 10 34 23 32.5 25.93 37 21 5 14 22 10 68 23.3 22.82 38 8 70 56 8 26 7 29.2 27.51 39 15 7 9 144 11 109 49.2 60.97 40 20 4 16 20 124 16 33.3 44.80 41 16 47 97 27 61 35 47.2 28.99 42 18 22 244 19 10 6 53.2 93.68 43 43 20 77 22 7 33 33.7 24.49 44 67 20 4 28 5 7 21.8 24.09 45 118 18 1 35 78 35 47.5 43.00 46 71 85 24 333 50 11 95.7 119.53 47 12 11 13 19 16 91 27.0 31.49 48 4 63 14 22 43 25 28.5 21.29 49 18 55 13 11 6 13 19.3 17.90 50 4 3 17 11 6 17 9.7 6.31