This table compares the used car price to the new car price of Ford cars.
This scatter diagram compares the new car price against the used car price of Ford cars. The trend line I added shows a slope going upwards from left to right. It shows a positive correlation between new car price and used car price. From the graph I can say that as the used car price increases the new car price increases. The equation of the line is:
y = 1.3597x + 6221
The gradient is 1.3597 and this tells us that every time the used car price increases by £1 the new car price will increase by £1.36. The intercept of the line is 6221 and this tells us that if the used car price is £0 then the new car price will be £6221.
This table shows the 9 Vauxhall cars out of 13 which were chosen using stratified sampling. It shows the mileage, the age, the used car price and the engine size.
This scatter diagram shows the affect on used car price as the age increases. The trend line I added shows a slope going downwards from left to right. It shows a negative correlation between used car price and age. From the graph I can say that as the age increases the used car price decreases. The equation of the line is:
y = -824.32x + 9092.1
The gradient is -824.32 and this tells us that every time the age increases by 1 year the used car price will decrease by £824.32. The intercept of the line is 9092.1 and this tells us that if the age is 0 then the used car price will be £9190.40.
This scatter diagram shows the affect on used car price as the mileage increases. The trend line I added shows a slope going downwards from left to right. It shows a negative correlation between used car price and mileage. From the graph I can say that as the mileage increases the used car price decreases. The equation of the line is:
y = -0.0815x + 8218.6
The gradient is -0.0815 and this tells us that every time the mileage increases by 1 year the used car price will decrease by £0.0815. The intercept of the line is 8218.6 and this tells us that if the mileage is 0 then the used car price will be £8218.6.
This scatter diagram shows the affect on used car price as the engine size increases. The trend line I added shows a slope going upwards from left to right. It shows a positive correlation between used car price and engine size. From the graph I can say that as the engine size increases the used car price increases. The equation of the line is:
y = 4545.5x - 3470.8
The gradient is 4545.5 and this tells us that every time the engine size increases by 1 the used car price will increase by £4545.50. The intercept of the line is 3470.8 and this tells us that if the engine size is 0 then the used car price will be - £3470.80.
This table compares the used car price against the new car price of Vauxhall cars.
This scatter diagram compares the new car price against the used car price of Vauxhall cars. The trend line I added shows a slope going upwards from left to right. It shows a positive correlation between new car price and used car price. From the graph I can say that as the used car price increases the new car price increases. The equation of the line is:
y = 1.4914x + 5648.1
The gradient is 1.4914 and this tells us that every time the used car price increases by £1 the new car price will increase by £1.49. The intercept of the line is 5648.1 and this tells us that if the used car price is £0 then the new car price will be £5648.10.
This table shows the 8 out of 12 Rover cars chosen using stratified sampling. The table shows the mileage, age, used car price and the engine size.
This scatter diagram shows the affect on used car price as the age increases. The trend line I added shows a slope going downwards from left to right. It shows a negative correlation between used car price and age. From the graph I can say that as the age increases the used car price decreases. The equation of the line is:
y = -2192.4x + 16152
The gradient is -2192.4 and this tells us that every time the age increases by 1 year the used car price will decrease by £2192.40. The intercept of the line is 16152 and this tells us that if the age is 0 then the used car price will be £16152.
This scatter diagram shows the affect on used car price as the mileage increases. The trend line I added shows a slope going downwards from left to right. It shows a negative correlation between used car price and mileage. From the graph I can say that as the mileage increases the used car price decreases. The equation of the line is:
y = -0.1119x + 10420
The gradient is -0.1119 and this tells us that every time the mileage increases by 1 year the used car price will decrease by £0.1119. The intercept of the line is 10420 and this tells us that if the mileage is 0 then the used car price will be £10420.
This scatter diagram shows the affect on used car price as the engine size increases. The trend line I added shows a slope going upwards gradually from left to right. It shows a positive correlation between used car price and engine size. From the graph I can say that as the engine size increases the used car price increases. The equation of the line is:
y = 1794.5x + 1546.8
The gradient is 1794.5 and this tells us that every time the engine size increases by 1 the used car price will increase by £1794.50. The intercept of the line is 1546.8 and this tells us that if the engine size is 0 then the used car price will be £1546.80.
This table compares the used car price against the new car price of Rover cars.
This scatter diagram compares the new car price against the used car price of Rover cars. The trend line I added shows a slope going upwards from left to right. It shows a positive correlation between new car price and used car price. From the graph I can say that as the used car price increases the new car price increases. The equation of the line is:
y = 0.5043x + 13304
The gradient is 0.5043 and this tells us that every time the used car price increases by £1 the new car price will increase by £0.5043. The intercept of the line is 13304 and this tells us that if the used car price is £0 then the new car price will be £13304.
This table shows the 7 out of 10 cars which were chosen using stratified sampling. The table shows the mileage, age, used car price and engine size of Fiat cars.
This scatter diagram shows the affect on used car price as the age increases. The trend line I added shows a slope going downwards from left to right. It shows a negative correlation between used car price and age. From the graph I can say that as the age increases the used car price decreases. The equation of the line is:
y = -661.55x + 6391.7
The gradient is -661.55 and this tells us that every time the age increases by 1 year the used car price will decrease by £661.55. The intercept of the line is 6391.7 and this tells us that if the age is 0 then the used car price will be £6391.70.
This scatter diagram shows the affect on used car price as the mileage increases. The trend line I added shows a slope going downwards from left to right. It shows a negative correlation between used car price and mileage. From the graph I can say that as the mileage increases the used car price decreases. The equation of the line is:
y = -0.0631x + 5012.8
The gradient is -0.0631 and this tells us that every time the mileage increases by 1 year the used car price will decrease by £0.0631. The intercept of the line is 5012.8 and this tells us that if the mileage is 0 then the used car price will be £5012.80.
This scatter diagram shows the affect on used car price as the engine size increases. The trend line I added shows a slope going upwards from left to right. It shows a positive correlation between used car price and engine size. From the graph I can say that as the engine size increases the used car price increases. The equation of the line is:
y = 3081.3x - 431.13
The gradient is 3081.3 and this tells us that every time the engine size increases by 1 the used car price will increase by £3081.30. The intercept of the line is 431.13 and this tells us that if the engine size is 0 then the used car price will be -£431.13.
This table compares the used car price and new car price of Fiat cars.
This scatter diagram compares the new car price against the used car price of Fiat cars. The trend line I added shows a slope going upwards from left to right. It shows a positive correlation between new car price and used car price. From the graph I can say that as the used car price increases the new car price increases. The equation of the line is:
y = 0.682x + 5823.6
The gradient is 0.682 and this tells us that every time the used car price increases by £1 the new car price will increase by £0.682. The intercept of the line is 5823.6 and this tells us that if the used car price is £0 then the new car price will be £5823.60.
Overall from looking at these scatter diagrams I have realised that the used car price is affected by different factors such as mileage, age, engine size. Each one of these factors produced similar scatter diagrams with similar trend lines for each car make.
Comparing 2nd hand prices of Renault and Vauxhall cars
I constructed this table so that I can make two box and whiskers which compare the second hand price of Renault and Vauxhall cars.
From the box plots I can see that Vauxhall cars have greater median price of second hand cars. This make also has a wider range of second hand prices. The Vauxhall also has a higher inter quartile and upper quartile range. This suggests that the cars are not made for the same market as there is a big difference in second hand price. The most expensive car for Vauxhall is £7999 where as the most expensive Renault was £6999. The least expensive Vauxhall was £850 but the least expensive for Renault was higher at £1495. This tells me that there is a wider price range for Vauxhall cars. What I see here may not be the same on the population as the sample is very small and also I had used more Vauxhalls then Renaults.
Comparing the second hand price of Ford and Fiat cars
I constructed this table so that I can make two box and whiskers which compare the second hand price of Ford and Rover cars.
From the box plots I can see that Ford cars have greater median price of second hand cars. This make also has a wider range of second hand prices. The Ford also has a higher inter quartile and upper quartile range. This suggests that the cars are not made for the same market as there is a big difference in second hand price. The most expensive car for Ford is £7999 where as the most expensive Rover was £6795. The least expensive Ford was £850 but the least expensive for Rover was higher at £1295. This tells me that there is a wider price range for Ford cars. What I see here may not be the same on the population as the sample is very small and also I had used more Fords then Rovers.
Comparing the second hand price of Renaults and Rover cars
A box and whiskers plot comparing
Second hand price of Rovers
and Fords
From the box plots I can see that the cars have a similar range. The most expensive car for Rover was £6795 where as the most expensive Renault was £6999. The least expensive Renault was £1495 but the least expensive for Rover was higher at £1295. The median of the Renault cars is slightly higher than Rover cars by £252. The lower quartile of the Rover was £1400 which was lower then the Renault which was at £1745. The Renault also had a higher upper quartile by £799. The price difference has been similar for these two cars which suggest that these two cars are aimed for similar markets. What I see here may not be the same on the population as the sample is very small and also I had used more Rovers then Renaults.
Comparing the second hand prices of Ford and Fiat cars
A box and whiskers plot comparing
second hand price of Fords
and Vauxhall
From the box plots I can see that the cars have the same range. The most expensive Vauxhall and Ford car was £7999. The least expensive Ford and Vauxhall were also the same at £850. The median of the Ford cars is slightly higher than Vauxhall cars by £405. The lower quartile of the Ford was £3000 which was lower then the Vauxhall which was at £3045.50. The Ford had a higher upper quartile by £205. The price difference has been similar for these two cars which suggest that these two cars are aimed for similar markets. What I see here may not be the same on the population as the sample is very small and also I had used more Rovers then Renaults.
Comparing depreciation rates of the five cars
The Rover car price depreciated the fastest as it has the highest gradient of 5592.4.
Average price of a 1 year old car:
This graph below shows me that the general trend is that the average price of the car decreases the higher the age of it is. There are some anonymous results. This is due to some cars which didn’t depreciate as much as expected. For example, the 8 year old car had a higher price then cars that ranged between 3-7 years old. This is an odd result so I searched what caused this result. The reason for this was because a ‘Bentley TurboR’ had the price of £37995 even after 8 years. This caused the average price to go up. Also for 9 years the average price is £4318.80 which is higher then the average price for cars that are 6 or 7 years old. This was due to a ‘Rolls Royce Silver Spirit’ which was priced at £14735.
Conclusion
Overall form looking at my results I have found out that there are many different factors that influence the price of second hand cars. My sample was very useful as it allowed me not to be bias in the cars I choose. Also looking at information from a scatter diagram made it easy to make relationships between the second hand price and factors which affect it. I feel that the sample was not as accurate as I had used more cars for some makes than others. From this I saw that the factor which had the most affect on second hand price was age and engine size of the car. To work this out I looked at the gradient of the line on my scatter diagram and compared them. The age and engine size had the steepest line so they had the greatest affect on second hand price. For most factors the correlation of between the population and sample were weak because the sample was not big enough to represent the population. The tend line can be used to predict the future price of the car as each factor changes. When comparing the makes I learnt that each factor had similar affect on different cars. The cheapest car to buy from the cars in my sample was a Vauxhall Cavalier which was £850. The car which depreciated the most over the years was Rovers as the trend line on the scatter diagram had the steepest gradient. All my hypotheses were right which I stated before I started the project. The weakness of this project is that my sample was not big enough for the population of cars that are in the U.K right now which are millions. So next time if I was to do this project again I would use a bigger sample to make my results and predictions more reliable.