In reviewing the data in the Performance Lawn Equipment Database, Elizabeth Burke noticed that defects received from suppliers have decreased $($worksheet Defects After Delivery. Upon investigation, she learned that in $2014,$ PLE experienced some quality problems due to an increasing number of defects in materials received from suppli. ers. The company instituted an initiative in August $2015$ to work with suppliers to reduce these defects, to more closely coordinate deliveries, and to improve materials quality through reengineering supplier production policies.

Ms$.$ Burke noted that the program appeared to reverse an increasing trend in defects, she would like to predict what might have happened had the supplier initiative not been implemented and how the number of detects might further be reduced in the near future.

In meeting with PLE's human resources director, Ms$.$

Burke also discovered a concern about the high rate of turnover in its field service stall, Senior managers have suggested that the department look closer at its recruiting policies, particularly to try to identify the characteristics of individuals that lead to greater retention. However, in a recent staff meet$-$ing. HR managers could not agree on these characteristics. Some argued that years of education and grade point averages were good predictors. Others argued that hiring more mature applicants would lead to greater retention. To study these factors, the staff agreed to conduct a statistical study to determine the effect that years of education, college grade point average, and age when hired have on retention.

A sample of $40$ field service engineers hired ten years ago was selected to determine the influence of these variables on how long each individual stayed with the company. Data are

compiled in the Eimployee Retention worksheet.

Finally, as part of its efforts to remain competitive, PLE tries to keep up with the latest in production technol ofy. This is especially important in the highly competi. tive lawn mower line, where competitors can gain a real advantage if they develop more cost$-$effective means of production. The lawn mower division therefore spends a great deal of effort in testing new technology. When now

$15$:$0311$: Trendlines and Regression Analysis

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production technology is introduced, firms often experi ence learning, resulting in a gradual decrease in the time required to produce successive units. Generally, the rate of improvement declines until the production time lev. els off. One example is the production of a new design for lawn mower engines. To determine the time required to produce these engines, PLE produced $50$ units on its production line; test results are given on the worksheet Engines in the database. Because PLE is continually developing new technology, understanding the rate of learning can be useful in estimating future production costs without having to run extensive prototype trials, and Ms$,$ Burke would like a better handle on this.

Use trendlines and regression analysis to assist her in evaluating the data in these three worksheets and reaching useful conclusions. Summatize your work in a formal report with all appropriate results and analyses.