Histograms summarize process data over a period of time, and present frequency in the form of a bar graph. Histogram GraphicA histogram:

  • Displays large amounts of data in visual format
  • Shows relative frequency of various data values
  • Illustrates underlying distribution of the data
  • Reveals the shape and variation of the data
  • Provides information for predicting future performance

How to Construct a Histogram

Creating a Histogram

  • Decide on the indicator to be measured
  • Collect at least 50 data points
  • Prepare a frequency table from the data
  • Group the data into intervals
  • Create the histogram

Interpreting a Histogram

  • Consider where the distribution is centered
  • Analyze the variation and spread of the data
  • Look at the shape of the distribution
  • Consider these factors in the context of targets

Further Reading

More Information

Icon PQ Systems: Histogram (PDF: 51KB / 6 pages)
Icon McCoy: Finding the Right Tool for your Purpose (PDF: 466KB / 40 pages)


Icon Public Health Memory Jogger
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