# Thread: Calculate contribution weight of an average

1. ## Calculate contribution weight of an average

My data set is looking at a bunch of rental car transactions. I grouped all the rentals together by what type of vehicle was rented. I have the numbers of rentals (how many times a vehicle was rented), Number of rental days (how many calendar days the rental went out for) , and the total amount it cost for the entire rental. From that I calculate the the average amount per calendar day it cost the rent a certain vehicle ( Total Rental Amount / number of rental days). I am comparing two calendar years (2015 & 2016).

What I need to get is the dollar amount each vehicle contributed to the total average growth year over year.

An example of what it would look like if below ( these are not correct, just to show what the outcome would look like

Thanks for any help. Excel Sheet is attached

2. ## Re: Calculate contribution weight of an average

Hey Terriault.

I'd recommend setting up a conditional expectation with a linear model.

If you have a value of growth for each year as a function of year with a linear model [possibly generalized depending on the model parameters and constraints] then you can estimate the growth random variable as a function and plot it.

What experience do you have with linear models and statistics?