Chap 2: Graphical descriptive methods

[...]... Australia, 1992–2009 Trend in total exports, Australia, 1992–2009 23 2.3 Graphical Techniques for Numerical Data There are several graphical methods that are used when the data are numerical (i.e quantitative, non-categorical) The most important of these graphical methods is the histogram The histogram is not only a powerful graphical technique used to summarise interval data, but it is also used to... and – a sample selected from the population 15 Graphical techniques for nominal data • The graphical presentations shown here are used primarily for nominal data • These graphical tools are most appropriate when the raw data can be naturally categorised in a meaningful manner 16 Bar charts • The bar chart is mainly used for nominal data • A bar chart graphically represents the frequency of each category... 13 2.2 Graphical and tabular techniques for nominal data The only allowable calculation on nominal data is to count the frequency of each value of the variable We can summarise the data in a table that presents the categories and their counts called a frequency distribution A relative frequency distribution lists the categories and the proportion with which each occurs 14 Introduction • The methods . data. Data Statistics Information 3 Populations and Samples The graphical and tabular methods presented here apply to both entire populations and samples drawn from populations. Population Sample Subset 4 Definitions… A. data are also called qualitative or categorical. Nominal Data… 8 Ordinal Data • Ordinal data appear to be categorical in nature, but their values have an order; a ranking to them: E.g. University. categories and the proportion with which each occurs. 14 Introduction • The methods presented apply to both – the entire population, and – a sample selected from the population. 15 Graphical