Bar Charts

Bar Charts Example A group of 30 university students were asked how many units of alcohol they drink each week. Their responses are shown in the column on the right. Construct a bar chart to illustrate this information. Units drunk each week Total 0- 5 5-9 2 10-14 12 15-19 6 20-24 3 25+

1. Drawing the axes The first step is to draw the two axes for your bar chart, these will show the two variables you are measuring. To work this out, look at your data – in this case you are measuring the number of units drunk and the number of students, these are therefore your two axes.

Input data: Next, input your data to the chart. Do this by drawing horizontal lines – bars – of the correct length to represent your data. If 5 students drank 0-4 units the line should reach as far as 5 on the horizontal scale.

What CAN we tell from Bar Charts If you look back at our bar chart, you will see that it shows clearly that 10 – 14 units was the most frequent response amongst our students, whereas 5-9 units and 25+ units were the least frequent. If you want to be really fancy, you might be able to say things like: “Roughly twice as many students drank 10-14 units as 15-19 units.”. Imagine you were given the bar chart without the original data. Can you say how many students drank 25 or more units? Yes, 2. You will see this is different compared to using a pie chart, which is the next lesson.