Refer to the Mining Engineering (Oct. 2004) study of a new technology for producing high-quality iron nuggets directly from raw iron ore and coal, Exercise 10.25. For one phase of the study, the percentage change in the carbon content of the produced nuggets was measured at 4-hour intervals for 33 consecutive intervals. The data for the 33 time intervals are listed in the table. Construct and interpret a variable control chart for the data. Is the process in control?

Data from Exercise 10.25

An innovative new ironmaking technology (called ITmk3) produces high-quality iron nuggets directly from raw iron ore and coal. Mining Engineering (Oct. 2004) published the results of pilot tests conducted on the new process. For one phase of the study, the carbon content produced in a pilot plant test was compared to that from laboratory furnace tests. The data for 25 pilot tests are listed in the table.

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CARBON2 Interval Carbon Change (%) Interval Carbon Change (%) 1 3.25 18 3.55 3.30 19 3.48 3 3.23 20 3.42 4 3.00 21 3.40 5 3.51 22 3.50 6. 3.60 23 3.45 3.65 24 3.75 8 3.50 25 3.52 3.40 26 3.10 10 3.35 27 3.25 11 3.48 28 3.78 12 3.50 29 3.70 13 3.25 30 3.50 14 3.60 31 3.40 15 3.55 32 3.45 16 3.60 33 3.30 17 2.90 7.