One step in the manufacture of large engines requires that holes of veryprecise dimensions be drilled. The tools that do the drilling are regularly examined and are adjusted to ensure that the holes meet the required specifications. Part of the examination involves measurement of the diameter of the drilling tool. A team studying the variation in the sizes of the drilled holes selected this measurement procedure as a possible cause of variation in the drilled holes. They decided to use a designed experiment as one part of this examination. Some of the data are given in the table below. The diameters in millimeters (mm) of five tools were measured by the same operator at three times (8:00 A.M., 11:00 A.M., and 3:00 P.M.). Three measurements were taken on each tool at each time. The person taking the measurements could not tell which tool was being measured, and the measurements were taken in random order.
(a) Make a table of means and standard deviations for each of the 5 × 3 combinations of the two factors.
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(b) Plot the means and describe how the means vary with tool and time. Note that we expect the tools to have slightly different diameters. These will be adjusted as needed. It is the process of measuring the diameters that is important.
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(c) Use a two-way ANOVA to analyze these data. Report the test statistics, degrees of freedom, and P-values for the significance tests.
(d) Write a short summary of the results
(e) Multiply each measurement by 0.04 to convert from millimeters to inches. Plot the means and run a two-way ANOVA using the transformed measurements. Summarize what parts of the analysis have changed and what parts have remained the same.