Used Car Prices - What affects them?

GCSE: Maths

I have been asked to investigate what affects the price of a second hand car. I have decided, firstly, to use the price depreciation rather than simply the second hand price. This will allow us to group all of the data completely as we won’t have to separate the data into different price ranges (this will be very helpful later on). More importantly, the cars would have begun with different prices, so the second-hand cost would have changed proportionally to the original price. We wanted to eliminate this factor as it is not fair and would lead to possible bias towards a certain price range of car.
We have been given details on 100 cars. I have gone and found another 100 to add to this; the more data we have, the less bias there is likely to be.
I will firstly find the price depreciation for all of the cars so that they will be easily accessible later on. Then, I will have a brief hypothesis stating what I believe will occur. I will then discuss possible causes of error and I will discuss how my sampling methods would make the test fairer. I will next include a pre-test of no more than 5 pages. This will show us which factors to take into account in the main test and will give us a vague idea of what will and what will not work, and is good as it doesn’t waste too much time. I will, upon seeing my pre-test results, then work out what size sample to use and how many strata to have. I will then go on with the main test and hope to find connections. In my main test I will take multiple samples from the data and put the selected cars from each stratum into tables and graphs to see if there is a connection between certain factors and price depreciation.
As aforementioned, firstly, I will put all the cars into a table showing the car number, price when new, price now and price depreciation for each. This will help later in the task for quick and easy access to all of the price depreciations. To find the price depreciation for each car, I must subtract the “Price Now” from the “Price When New” and then divide by the “Price When New.” Finally, multiply by 100 ….. (New – Now) ÷ New x 100
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