• A simple classic, the histogram uses stacked oblongs to represent volume, value, percentage, or any other quantities that require comparison.
• Traditionally, the highest value is placed on the left, with the remainder ranked in descending order to the right.
• The left hand vertical axis should be given a clear and accurate scale.
• If all the data is a snapshot of one moment in time, then the horizontal axis can be left unlabelled.
• Histograms can also be used to show data over time, with each block denoting a time period such as a day, week, month or year.
• If you are drawing a time-based histogram, then the units of time need to be clearly labelled on the horizontal axis, as in Jan, Feb, Mar, etc.
Exercise: Choose a ...