$8$: Trendlines and Regression Analysis

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 suppliers. 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 defects might further be reduced in the near future.