1. Histograms: A Valuable Tool for Quality Evaluation
By Perry Katz
This is the opening slide. It serves to tell my audience what kind of information that I will be discussing. This slide clearly states that I will be discussing the topic of Histograms.
4/3/2019

2. Overview What is a Histogram?
What are some possible uses for a Histogram?
Where did the Histogram come from?
How do Histograms work?
A real world example.
An exercise.
This slide serves to give an overview, or outline, of the information that I will discuss. It gives my audience a step-by-step plan that they can follow, so that they always know where we are, and where we are going next in the tutorial.
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3. What is a Histogram?
A Histogram is a variation of a bar chart in which data values are grouped together and put into different classes.
This grouping allows you see how frequently data in each class occur in the data set.
This slide is basically the beginning of my tutorial. I start off with the explanation of what exactly a Histogram is. A Histogram is a variation of a bar chart in which data values are grouped together and put into different classes. This grouping allows you see how frequently data in each class occur in the data set.
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4. What is a Histogram (cont.)
Higher bars represent more data values in a class.
Lower bars represent fewer data values in a class.
On the next slide is an example of what a Histogram looks like.
This slide gives further explanation about what a Histogram is. I explain the relationship between the height of the bars in the Histogram, to the amount of data values in each class. More data values mean taller bars. The opposite would be true for fewer data values, meaning lower bars for fewer data values. Next is a simple example of what a histogram might look like.
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5. Example of a Histogram 4/3/2019
This is a simple example of what a Histogram looks like. This gives my audience at least some picture of what a very basic histogram would look like.
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6. Uses for a Histogram A Histogram can be used:
to display large amounts of data values in a relatively simple chart form.
to tell relative frequency of occurrence.
to easily see the distribution of the data.
to see if there is variation in the data.
to make future predictions based on the data.
Here, I name some of the uses for a Histogram. I tell what makes this tool useful in making quality improvements. Since the histogram is such a useful tool, it can have many uses. Histograms can be used to display large amounts of data in a simple chart view. They can be used to find any patterns that the data might reveal. They can be used to tell relative frequency of occurrence for certain data values. They can also be used to see the distribution, or any variations in the data values. One other use would be to make predictions regarding the future based on the way the data values pan out.
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7. Where did the Histogram Come From?
The Histogram was first implemented by Kaoru Isikawa, one of Japans’ most renowned experts on quality improvement.
Isikawa spent his life trying to improve quality in Japan.
This slide serves to give my audience some idea of where the Histogram came from. I tell a little bit about Isikawa and what he was about. Then I tied in his development of the Histogram. Kaoru Ishikawa was a pioneer in quality improvement, not only for Japan, but for the rest of the world as well. Although his practices weren’t very highly regarded in the U.S., any company that seeks to improve quality would ultimately have to use his practices. This is what makes his work so important.
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8. Where did the Histogram Come From? (cont.)
His major contributions to quality improvement are known as the basic seven tools of quality.
Included in his basic seven tools of quality is the Histogram.
This slide goes right along with the previous one. It explains that the Histogram was developed by Ishikawa, along with the other basic seven tools of quality. These tools were the major contribution of Ishikawa to the quality improvement community. The other six tools include Pareto Charts, Cause and Effect Diagrams, Check Sheets, Scatter Diagrams, Flowcharts, and Control Charts.
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9. How do Histograms Work?
First, you need need to pick a process to analyze.
Next, you need a large amount of data, at least 100 data values so that patterns can become visible.
Then, you need to assemble a table of the data values that you collected with regards to frequency of data values.
Histograms are a valuable tool for quality improvement, as long as you know how to use them properly. First, you have to pick a process that you would like to measure. This can be anything from number of items output per week, to the number of calls incoming per day. Basically anything that occurs over an extended period of time. You need to be able to collect a whole lot of data for a histogram, at least 100 data values. The more data values, the better. After you collect all of your data, you need to assemble a table of data values. The important thing here is that you must take into account the frequency of data values.
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10. How do Histograms Work? (cont)
Next, you need to calculate some statistics for the Histogram, including: mean, minimum, maximum, standard deviation, class width, number of classes, skewness, and kurtosis.
Then, you actually create the Histogram using these statistics.
The next part in using a Histogram is to calculate some statistics so you can make a chart. You need to calculate the mean, minimum, maximum, standard deviation, class width, number of classes, skewness, and kurtosis. Mean is the average of all values. Minimum is the smallest value. Maximum is the biggest value. Standard Deviation is how widely spread the values are around the mean. Class Width is the x-axis distance between the left and right edges of each bar in the histogram. Number of Classes is the number of bars in the Histogram. Skewness is the alignment of the Histogram. Kurtosis is a measure of the pointiness of the distribution. After you calculate these statistics, you can create the actual histogram.
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11. How do Histograms Work? (cont)
After you have created a Histogram, it will take one of five shapes:
Normal Distribution:
The five shapes that a histogram could take include: normal distribution, positively skewed, negatively skewed, bi-modal distribution, and multi-modal distribution.
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12. How do Histograms Work? (cont)
Positively Skewed:
Negatively Skewed:
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13. How do Histograms Work? (cont)
Bi-Modal Distribution:
Multi-Modal Distribution:
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14. How do Histograms Work? (cont)
Once your Histogram is complete, you can analyze its shape, as well as the statistics that you came up with.
This analysis will help you to make better decisions toward quality improvements.
After completing the Histogram, its’ use as a tool for quality improvement can be seen. You can look at the completed histogram and analyze its’ shape. Along with the statistics that you calculated, you can get a good idea of where any problems might be, or where to make any changes to the process.
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15. Real World Example
The next slide contains a real world example of a histogram. It plots the relative frequency of the heights of some students based on the data below.
                             Frequency: Height (feet):          (Number of pupils)     Relative frequency: 0-2                        0                                0 2-4                        1                                1 4-5                        4                                8 5-6                        8                                                        2                                2
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16. Real World Example
This is a fairly simple histogram. It plots the relative frequencies(how many students are at each height) and the actual heights. From this we can see that most of the students are between five and six feet tall. Many fewer students are between two and four feet, as well as between six and eight feet tall. A decision that could me made from this might be to make the doorways in the new school higher than seven feet, so that everyone could be accommodated. But once again, this is a very simple histogram
This Histogram is courtesy of
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17. Exercise
A great exercise which would help you better understand what a histogram is all about can be found at :
Here you are walked through the making of a histogram. You see all of the aspects that I have discussed in this tutorial.
This exercise on the web is much better than any exercise I have seen. It allows the user to see all of the important parts of a Histogram. The user can be walked through the making of the histogram, this allows the user to better understand what a Histogram is all about, and how it can be applied to real life quality problem.
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18. Summary
After going through this tutorial you should have a better idea of:
What a Histogram is.
What a Histogram is used for.
Where the Histogram came from.
How Histograms work.
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19. Histograms: A Valuable Tool for Quality Evaluation
By Perry Katz
This is the closing slide. It serves to tell my audience what kind of information that I covered. This slide clearly states that I have discussed the topic of Histograms.
4/3/2019