Data Presentation
What graphs and diagrams should I be familiar with?
- You will be expected to be able to use a variety of graphs such as:
- Stem-and-leaf diagrams
- Can be used with ungrouped data of a single variable
- Shows all the data and the shape of its distribution
- Box plots
- Can be used with ungrouped data of a single variable
- Shows the range, interquartile range and quartiles clearly
- Very useful for comparing data patterns quickly
- Cumulative frequency graphs
- Can be used with continuous grouped data of a single variable
- Shows the running total of the frequencies that fall below the upper bound of each class
- Histograms
- Can be used with continuous grouped data of a single variable
- Can be used with varying group sizes
- Shows the frequencies of the group, represented by the area of each bar
- Stem-and-leaf diagrams
- You might be expected to draw a full diagram or to add to an incomplete diagram
What should I look out for when interpreting graphs?
- Look carefully at the context of the information given in the graph
- Check the scales on both axes carefully, including units
- Sometimes the numbers will be abbreviated to fit on the scale, for example if a population is given in millions then the number 60 will represent 60 000 000
- Look carefully at the labels and units to determine how a value should be read
- If there is more than one graph represented on the same set of axes take extra care to ensure you are reading from the correct one
- Beware of misleading graphs, the scales on the axes, units and representation can be manipulated to make a graph look more/less convincing
Exam Tip
- Take the time needed when working with diagrams, they are usually ‘easy marks’ questions but it is common for students to rush them and make silly mistakes.
