Presentation of quantitative data tables and graphs

• Bar charts:

  • data can be represented visually using a suitable graphical display so the difference in mean values can be easily seen
  • the most suitable graph in this case is a bar chart
  • bar charts are used when data is divided into categories, otherwise known as discrete data
  • the categories are conditions, and these occupy the horizontal x-axis
  • the frequency or amount of each category is plotted on the vertical y-axis
  • bars are separated on a bar chart to denote that we are dealing with separate conditions
• Histograms:

  • in a histogram, the bars touch each other, which shows the x-axis data is continuous rather than discrete
  • the x-axis is made up of equal-sized intervals of a single category
  • the y-axis represents the frequency within each interval
  • if there was a zero frequency for one of the intervals, the interval remains but without a bar
• Scattergrams:

  • unlike the other forms of graph, scattergrams do not depict differences but correlations between co-variables
  • either of the co-variables occupies the x-axis and the other the y-axis and each point on the graph corresponds to the x and y position of the co-variables
• Line graphs:

  • line graphs, like histograms, represents continuous data and use points connected by lines to show how something changes in value e.g. over time
  • typically the independent variable is plotted on the x-axis and the dependent variable on the y-axis