Histogram (Frequency Distribution)

A histogram, sometimes called a frequency plot or frequency distribution, graphically shows the distribution of a data set–including display of central location (mean, median, and mode), shape, and spread of data.  It is often used in combination with a run or control chart to further study process performance.  It can also be used when the sequencing of data has not been preserved.  The X axis is built of several consecutive groupings, called cells, using continuous data like time, weight, size, or temperature.  The Y axis is typically a count or percent within each cell.


The reader is referred to the Institute for Healthcare Improvement’s website for complete instructions and another example.


Executive Learning, Inc. Handbook for Improvement: A Reference Guide for Tools & Concepts. ELI, 2002, 147-151.
GOAL/QPC, The Memory Jogger. GOAL/QPC, 1994, pp. 66-75.
Murray, Sandra K. & O. Bryan Murray. Practical Tools for Healthcare Quality:Total Quality Transformation. PQ Systems, 1997, 107-125.

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