Histogram
What is it?
The Histogram is a bar graph of raw data. The bars represent the frequency of occurrence by classes of data. The histogram shows basic information about the data set, such as central location (mean, median, mode), width of spread (range or standard deviation), and the shape.
With the histogram one can gain knowledge about a
system. Knowledge gained from the basic
information given by the histogram can aid in improving the system. A team uses the histogram to assess a
system’s current situation and to study results. The histogram’s shape and
statistical information help the team know how to improve the system. After a countermeasure is implemented, the
team continues to gather data and make histograms to monitor the effectiveness
of the countermeasure.
Why is the
Histogram used?
1.
To
compare data sets of related value.
2.
To
display central location, shape and the spread of the data.
How is the
Histogram used?
1.
Select
the classes by determining the number of classes and the classes' width .
2.
Record
the data by creating a check sheet which list the classes along the left side
and tally marks of occurrences along the right. Total the number of tally marks in each class.
The following example of a Histogram is based on the
values from our Check Sheet.
|
Category |
Frequency |
Total |
|
Unexcused absences Drug and alcohol abuse Tardiness Illegal parking Dress code violation Vandalism Class disruption Fighting and assaults Speaking out of turn Total |
lllll lllll lllll lllll lllll lll lllll ll lllll lllll lllll lllll lllll lllll lll ll l ll lllll lllll lllll llll lllll lllll lll |
28 7 33 2 1 2 19 10 3 105 |
