Presentation and Display of Quantitative Data: Graphs and Tables

What are graphs used for?

Graphs are used to illustrate the findings of studies and make data easy to read. Graphs should be simple and clear and appropriate for the data you have. Graphs should always include an appropriate title which includes the variables of the study.

Bar charts

• show data in the form of categories (disrcrete data) that the researcher wishes to compare (e.g. males, females)

• The bars must be the same width and separated by a space because the data are discrete

• The x-axis should be labelled with categories ; the y axis should be labelled with ‘frequency’ or ‘Number of…’

• Used for nominal data (non-numerical categories)

What does a bar chart look like?

Histograms

• Show data where both variables follow the numbered scale (continuous data) (e.g. time, height, test score).

• In a simple histogram the bars can be the same width; in a complex histogram the bars widths can vary. There must be no space between the bars because the data are continuous

• The x-axis should be labelled with numbers (or numerical groups); the y-axis on a simple histogram should be labelled with ‘frequency’ of ‘Number of…’

What does a histogram look like?

Scattergrams

• display findings of correlational studies

• The x-axis and y-axis should be labelled with the co-variables

• A dot/cross is plotted to indicate the value of each co-variable. A line of best fit can be drawn but is not necessary

How does a scattergram look?

Tables

• tables are used to summaries raw data and typically include a measure of central tendency and measure of dispersion. They should be clearly labelled and easy to read.

How do tables look?