The nine year old cars are shown below.

The ten year old cars are shown below.

The average price of cars at each age is shown below.

The information is shown below in the form of a line graph. I chose to use a line graph as this is the best way to display the data as it shows patterns and trends.

I have removed the anomalous result and redrawn the graph.

I have also plotted all of the results on a scatter diagram shown below.

Interpret and discuss

A line graph was drawn using the averages of the different years.

There is an anomalous result at eight years, as a Bentley car was particularly expensive and this is making the average much higher.

The line graph shows that generally the older a car get the less it costs.

The line graph shows a general trend in the results but isn’t that accurate. So I plotted all the data into a scatter diagram with line of best fit. The three anomalous results where removed from the data before the diagram was drawn.

If I was to repeat this question I would use all the data the first time or use a larger random sample.

I think the scatter diagram was particularly good although the line graph shows trends and patterns in the data, but isn’t very accurate.

Does the mileage of second hand cars affect the price?

Plan

I am going to find out whether the mileage of second hand cars affects the price.

Firstly I will separate the price and mileage from the rest of the data.

I will take a random sample of the data using the random number generator on the calculator, thirty random numbers will be generated then the corresponding cars will be separated from the data. I have chosen thirty cars because this is an adequate sample approximately one third of the data.

I am then going to use this data to plot a scatter diagram. A line of best fit will then be drawn in.

Collecting, Processing and Representing

Below is a table showing the price and the mileage of all the cars.

The following cars don’t have the mileage stated so will have to be left out of my results.

Below is a scatter diagram showing the price of cars and the mileage.

This scatter diagram is inconclusive, so I have redrawn a diagram with all the data. Four anomalous results where removed.

This diagram is more conclusive and more accurate as all the data is used.

Interpret and discuss

Generally there is a trend in the results the line of best fit shows that the higher the mileage the lower the value. The line of best fit was drawn by trying to get the same amount of points on each side of the line. The bar chart shows a trend the higher the lower the price the higher the mileage.

There are two anomalous results, one was the Bentley car, this is a particularly expensive car and the other is another similar car. This was not included in the line of best fit.

I gathered the information for the first scatter diagram by using random sampling. The random number generating key on a calculator and the corresponding piece of data was plotted on a scatter diagram.

The first diagram was inconclusive because of anomalous results and the size of the data used. I redrew the scatter diagram after any anomalous results where removed. This time all of the data was used. The scatter diagram was more conclusive and clearly shows, the higher the mileage the lower the value.

If I was to repeat this question I would have used a smaller sample of data e.g. half the data as the scatter diagram is a bit crowded.

The scatter diagram was a success and so was the bar chart as they both enabled me to see trends in the data.

Does the size of the engine on second hand cars affect the price?

Plan

I am going to find out whether the size of the engine affects the price.

To make the results as accurate as possible I am going to use all the data in my chart. I am going to display the data in the form of a scatter diagram as this will allow me to draw a line of best fit. I will also draw a pie chart to display the modal class.

I have chosen to use all the data in this scatter diagram as previously a sample of data hasn’t been sufficient to see trends in the data.

Firstly I will separate the engine size and the price from the rest of results. Secondly I will enter that data into a scatter diagram.

Collecting, Processing and Representing

I have plotted the above data below.

I am going to remove these anomalous results and then redraw the diagram as the above diagram is inconclusive a pattern can be seen but it is impossible to draw a line of best fit. .

Interpret and discuss

I used all the data to make my line of best fit as accurate as possible.

The modal class was 1.4 litres as shown above in the pie chart.

There where two anomalous results which weren’t included in the line of best fit. When drawing the line of best fit I tried to get the same amount of points on each side of the line.

The line of best fit shows a steady increase i.e. the bigger the engine the greater the price.

The scatter diagram and line of best fit clearly show that the size of the engine affects the price.

Generally in second hand cars the bigger the engine the higher the price.

I think the scatter diagram was a success as it allowed an accurate line of best fit to be drawn. Although the pie chart is unclear and if I was to repeat this question I might just include the top five categories.

The average cost of Vauxhall cars compared to Ford cars.

Plan

I am going to compare the average cost of Ford cars to the cost of Vauxhalls.

I chose these makes because these where the most common, in the data I found out this by tallying all of the makes of cars and these where the highest. This

I will also use the data to create a Cumulative Frequency diagram. This will enable me to accurately compare the results.

Collecting, Processing and Representing

I have tallied the amount of cars for each make, the chart is shown below.

Below is a doughnut diagram showing the top four makes of cars.

Below is the Ford and Vauxhall Data

The above diagram is not very accurate so I have used the data to create a cumulative frequency diagram.

excellent

Interpret and discuss

Ford and Vauxhall were the two most popular makes of car as shown above in the doughnut diagram. So I used these in the comparison.

A sampling method wasn’t used as there was only a small amount of data for each make of car.

The cumulative frequency diagram shows that generally Ford cars are a similar price to Vauxhalls. On some points of the Cumulative frequency Diagram Vauxhall is higher than Ford but at some points it is the opposite.

The box and whisker plot shows that the mean of the cars is very similar. There is a greater range of data about Ford cars, although it isn’t much different. Vauxhalls Mean, Lower Quartile and Upper Quartile is slightly higher than Fords but not significantly enough to make a comparison.

The scatter diagram comparing the two makes shows they are very similar.

It isn’t possible to say which car is the most expensive so I have come to the conclusion that:

Generally the price second hand Ford and Vauxhall cars is very similar, there aren’t any major differences in price.

If I was to repeat this question I wouldn’t do a scatter diagram as it is very difficult to draw accurate lines of best fit.

I am particularly proud of the Cumulative Frequency Diagram which compares the two sets of data.