Quality Improvement at MDH

Histogram

What is a Histogram?

Histograms summarize process data over a period of time, and present frequency in the form of a bar graph. Many histograms—if not most—are created using Microsoft Excel. Histograms allow a team to:

  • Display large amounts of data in visual format
  • Show relative frequency of various data values
  • Illustrate underlying distribution of the data
  • Reveal the shape and variation of the data
  • Provide information for predicting future performance

How to Construct a Histogram

  • Decide on the indicator to be measured
  • Collect a large number of data points (50+ is helpful)
  • Prepare a frequency table from the data
  • Group the data into intervals
  • Create the histogram

How to Interpret 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

More Information

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

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