(Solved by Humans)-PROBLEM 3–14 High–Low Method; Scattergram Analysis [LO2] Davidson Engine Repairs provides...

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  PROBLEM 3–14 High–Low Method; Scattergram Analysis [LO2] Davidson Engine Repairs provides maintenance and repair services for small engines such as those found in lawn mowers, power saws, and snow throwers. The repair shop costs include the salaries for the mechanics, insurance and depreciation on the repair equipment, materials and parts used for the jobs, and utilities. The repair shop manager would like to develop a model for predicting repair costs and over the past 10 months has carefully recorded the total repair       costs incurred, along with the number of maintenance and repair jobs completed each month. The data are shown below:   Month Jobs Repair Costs January . . . . . . . . . . . . . . . . . . . . . . 220 $22,000 February. . . . . . . . . . . . . . . . . . . . .   . 180 $ 18,000 March . . . . . . . . . . . . . . . . . . . . . . .  . 160 $ 17,600 April . . . . . . . . . . . . . . . . . . . . . . . . .  . 200 $20,000 May . . . . . . . . . . . . . . . . . . . . . . . . . . 260 $24,000 June . . . . . . . . . . . . . . . . . . . . . . . .   . 240 $22,400 July . . . . . . . . . . . . . . . . . . . . . . . . . . 140 $ 16,000 August. . . . . . . . . . . . . . . . . . . . . . .  . 120 $ 12,800 September . . . . . . . . . . . . . . . . . . . 100 $ 13,600 October . . . . . . . . . . . . . . . . . . . . .   . 80 $ 9,600 Required: 1.              Using Microsoft Excel, prepare a scattergram by plotting jobs performed and repair costs on a graph. Fit a straight line to the plotted points using the “add trendline” feature in Microsoft Excel. Do repair costs appear to be related to the number of jobs completed in a month? Explain. 2.              Using the high–low method, estimate a cost formula for repair costs. Express the formula in the form Y = a + bX. 3.              Now assume the manager wants to predict costs for a month where 600 jobs will be com- pleted. Should you use the formula developed above to predict costs for a 600-job month? Why or why not?