# The Percentage Decrase in Price of a Car and Its Mileage

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The Percentage Decrase in Price of a Car and Its Mileage

Aim

To find out if the mileage that a car has run is related in any way to

the percentage decrease in the price of the car from original price to

secondhand price.

This would be worthwhile doing as the mileage directly affects the

quality of the car and so, affects the price.

I will do a pretest (graph of everything) to ensure that the

investigation is worth doing, just to see if there is an overall

correlation.

Method

I will pick out the data I need for this project and take samples.

Here I will need the statistics of mileage and both prices then use

the spread sheet to work out the price decrease percentage.

I will test them for any relation they may have and draw scatter

diagrams.

The scatter diagrams would have lines of best fit.

A cumulative frequency table may also be useful in finding the

relations.

l Data

The information I need to collect are the prices and the mileage.

These are available in the excel spreadsheet from the KGV math site

and I will be working form this. The spread sheet is reliable as it is

provided for us. It contains a sample of 100 cars.

I will take three samples of 10 using stratified sampling (taking a

few from each 10) and leaving out the extremes from both ends. This

will give a fair sample as all the different percentages are taken

into account.

The samples will be compared to each other to find if there is a

correlation.

I will also find the correlation coefficient using the formulas:

âˆ‘ x;y - âˆ‘x; âˆ‘y âˆ‘ x2 - (âˆ‘x;)2 âˆ‘y;2 - (âˆ‘y;) 2

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Prediction

I think that there will be a strong positive correlation as usually,

the price drops by a greater percentage as the mileage increases.

Hypothesis

I think that this will be true as older cars get sold for less money.