WJEC Maths for AS: Applied sample

17 2.1 Interpreting diagrams for single variable data 2.1 Interpreting diagrams for single variable data (histograms, box and whisker, and cumulative frequency diagrams) Observations or measurements of a variable are called data. Data can be of two types: • Quantitative – where values (i.e. numbers) are given. • Qualitative – where the data is non numeric (e.g. very hard, hard, easy, very easy). Quantitative data can be further divided into discrete or continuous. Discrete data – data that can only take certain values (e.g. the number of children in a household can be 0, 1, 2, 3, etc.) and in a certain range. Continuous data – data that can take any value within a certain range. Single variable data graphs and charts use a set of measurements (i.e. variable values) and the number of times they occur (i.e. the frequency). There are a number of graphs/charts that can be used to display single variable data and these include: • Bar charts • Histograms • Pie charts • Box and whisker diagrams • Cumulative frequency curves. Bar charts Bar charts have qualitative data on one axis and frequency on the other. The following computer-produced bar chart shows the frequency on the vertical axis and the qualitative data (i.e. categories (pets in this case)) on the horizontal axis. Dog 70 60 50 40 30 20 10 0 Cat Guinea pig Rabbit Budgie Mouse Gerbil Parrot Hamster Fish Other animal Other bird Reptile Frequency In the actual exam, you would not be expected to draw graphs using graph paper, i.e. accurate representations of the data in a table, but you may be asked to sketch a graph, showing, for example, the shape of a distribution, or perhaps drawing a box plot and marking on any key values.