Johnson filtration, inc., provides maintenance service for water filtration systems throughout southern florida. customers contact johnson with requests for maintenance service on their water filtration systems. to estimate the service time and the service cost, johnson's managers want to predict the repair time necessary for each maintenance request. hence, repair time in hours is the dependent variable. repair time is believed to be related to three factors; the number of months since the last maintenance service, the type of repair problem (mechanical or electrical), and the repairperson who performs the repair (donna newton or bob jones). data for a sample of 10 service calls are reported in the following table.
repair time in hours months since last services type of repair repairperson
2.9 2 electrical donna newton
3.0 6 mechanical donna newton
4.8 8 electrical bob jones
1.8 3 mechanical donna newton
2.9 2 electrical donna newton
4.9 7 electrical bob jones
4.2 9 mechanical bob jones
4.8 8 mechanical bob jones
4.4 4 electrical bob jones
4.5 6 electrical donna newton
what is the impact of repair person on repair time when only the number of months since last maintenance service and the repair person are part of the model? explain.