To improve the quality of the output of any production process, it is necessary first to understand the capabilities of the process (Gitlow, Quality Management, 2004). In a particular manufacturing process, the useful life of a cutting tool is related to the speed at which the tool is operated. The data in the table below were derived from life tests for the two different brands of cutting tools currently used in the production process. For which brand would you feel more confident in using the least squares line to predict useful life for a given cutting speed? Explain.

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Useful Life (Hours) Cutting Speed (meters per minute) Brand A Brand B 30 30 30 4.5 3.5 5.2 6.0 6.5 5.0 40 40 40 50 50 5.2 4.0 2.5 4.4 2.8 6.0 4.5 5.0 4.5 4.0 3.7 50 60 1.0 4.0 2.0 1.1 1.1 .5 3.8 3.0 2.4 1.5 2.0 70 70 70 3.0 1.0