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Histogram
What is it?
A histogram is a diagram that graphically depicts the variability in a process
or procedure within your agency. When you want to see how a procedure is working
in your organization, you can gather data about that procedure (such as the
amount of time the procedure takes) and create a histogram. Then you can see
the variation in the amount of time it takes to do that process within your
organization.
Who uses it?
The team members, the managers.
Why use it?
Discovering and displaying this variation will greatly increase the team's knowledge
about a process.
When to use it?
When you want to see the pattern of variation of a particular process, such as
when you are describing a problem, or during data collection and
analysis.
How to use it:
The steps to create a histogram include:
- Gather the data about the variable you are interested in.
- Look at the data and determine the categories or intervals you will
use to organize the data. For example, if you are measuring the number of weeks it takes to receive an order of contraceptives, "number of weeks of waiting time" is the data category.
- Construct a frequency table for your data. The frequency corresponds to the number of times each value is observed. Using the example of waiting time to receive an order of contraceptives, the frequency table might look like this:
| Number of Weeks
of Waiting Time | Frequency |
| 1 week | I |
| 2 weeks | I |
| 3 weeks | IIII |
| 4 weeks | IIIII |
| 5 weeks | III |
| 6 weeks | I |
- To create the histogram, draw a horizontal and a vertical axis.
The horizontal axis (X) shows the data categories (such as time, or a
measurement, like weight). The vertical axis (Y) represents the frequency of the observations (the number of observations for each category).
- For each category of data, draw a rectangle (without space between the rectangles). The width of the rectangle represents the interval between two groups, and the height represents the observed frequency.
Example:
Here is an example of a histogram being used to describe the problem.
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