activity :-
students has to collect all the information related to data handling ( types of data handling , types of chart to compare data , suitable graph for different kind of data , purpose of choosing right chart for different data)
Answers
Types of Charts
There are several different types of charts and graphs. The four most common are probably line graphs, bar graphs and histograms, pie charts, and Cartesian graphs. They are generally used for, and are best for, quite different things.
You would use:
- Bar graphs to show numbers that are independent of each other. Example data might include things like the number of people who preferred each of Chinese takeaways, Indian takeaways and fish and chips.
- Pie charts to show you how a whole is divided into different parts. You might, for example, want to show how a budget had been spent on different items in a particular year.
- Line graphs show you how numbers have changed over time. They are used when you have data that are connected, and to show trends, for example, average night-time temperature in each month of the year.
- Cartesian graphs have numbers on both axes, which therefore allow you to show how changes in one thing affect another. These are widely used in mathematics, and particularly in algebra.
Axes
Graphs have two axes, the lines that run across the bottom and up the side. The line along the bottom is called the horizontal or x-axis, and the line up the side is called the vertical or y-axis.
- The x-axis may contain categories or numbers. You read it from the bottom left of the graph.
- The y-axis usually contains numbers, again starting from the bottom left of the graph.
The numbers on the y-axis generally, but not always, start at 0 in the bottom left of the graph, and move upwards. Usually the axes of a graph are labelled to indicate the type of data they show.
Beware of graphs where the y-axis doesn't start at 0, as they may be trying to fool you about the data shown (and there is more about this on our page, Everyday Mathematics).
Bar Graphs and Histograms
Bar graphs generally have categories on the x-axis, and numbers on the y-axis (but these are interchangeable). This means that you can compare numbers between different categories. The categories need to be independent, that is changes in one of them do not affect the others.
- You can see immediately that this graph gives you a clear picture of which category is largest and which is smallest. It gives a clear comparison between categories.
- You can also use the graph to read off information about how many are in each category without having to refer back to the data table, which may or may not be provided with every graph you see.
- In general, you can draw bar graphs with the bars either horizontal or vertical, because it doesn’t make any difference. The bars do not touch.
- A histogram is a specific type of bar chart, where the categories are ranges of numbers. Histograms therefore show combined continuous data.
Pictograms
A pictogram is a special type of bar graph. Instead of using an axis with numbers, it uses pictures to represent a particular number of items.
Pie Charts
A pie chart looks like a circle (or a pie) cut up into segments. Pie charts are used to show how the whole breaks down into parts.
- Pie charts, unlike bar graphs, show dependent data.
Cartesian Graphs
Cartesian graphs are what mathematicians really mean when they talk about graphs. They compare two sets of numbers, one of which is plotted on the x-axis and one on the y-axis. The numbers can be written as Cartesian coordinates, which look like (x,y), where x is the number read from the x-axis, and y the number from the y-axis.
Line Graphs
Line graphs are usually used to show dependent data, and particularly trends over time.
- Line graphs depict a point value for each category, which are joined in a line. We can use the data from the pie chart as a line graph too.