The machines on a given shop floor are of 3 types. The machines were acquired at different times so their age varies. The data in the file Machine Repairs.xls contain the recorded annual Cost of repairs, Age and Type for each machine.
i. Develop a regression model for the Cost, using as explanatory variables the Age and the Type of machine. Consider the interaction between Age and Type of machine as well.
ii. Perform the regression analysis and comment on the significance of the model and the explanatory variables.
iii. Excluding all variables that you consider non-significant, run the model again and interpret the coefficients.
iv. Based on the previous results, present the regression equations for each machine and the relevant data on one graph.
Machine Repairs file in the link: https://www.dropbox.com/s/3kg7u003ywp0xvb/Machine%20repairs.xls?dl=0