Edition 6: Journey into the basic quality tools - Histogram

Thank you for the connections who have subscribed to the newsletter. We are starting the series on Quality Tools after editions which shared the founding fathers of modern quality

This edition is on Histogram (one of the important key quality tool)

What is Histogram :

A histogram is one of the key basic quality tools and is a type of chart that plots the distribution of a numeric variable's values as a series of bars. Each bar typically covers a range of numeric values called a bin or class; a bar's height indicates the frequency of data points with a value within the corresponding bin.

Histogram is the appropriate graphical format to represent Continuous Data (Measurement Data such as dimensions of a product, weight, time etc). Histogram will have class intervals of the continuous data along the X axis. The scale for the frequency distribution (number of data points in the continuous data set which will fall in a particular class interval) will be along the Y axis. Adjoining bars will be constructed for each of the class interval coinciding with the frequency distribution scale on the Y axis. If we connect the midpoints of the adjoining bars in a Histogram, we will obtain a bell curve

How can you interpret the histogram:

1) Spread of the continuous data distribution (how much the continuous data set vary, ie. Distance between the maximum and minimum data points in a continuous data set can be ascertained through the width of the bell curve)

2) Shape of the data distribution - whether the data distribution is normal or skewed - if we get a symmetric bell curve we can conclude that the data distribution is normal. But if we get a bell curve which has a long tail either on the right hand side or left hand side, we would call the data distribution as skewed - if the bell curve has a longer tail on the right hand side it will be referred as positively skewed and if it has a longer tail on the left hand side then the bell curve is negatively skewed - Skewed data distributions are non-normal distributions.

3) We can identify the class interval which is likely to contain the average value. The class interval with the tallest bar is likely to contain the average value as most of the data points in the data set would fall in this class interval.

The interpretation of data mapped is important and we need to spend time to analyze and come with findings as we have too much data and fancy slides, but we miss the details and go behind something which might not give you the best return.

Where can you use the chart?

The histogram practically can be used across industries and for outsourcing industry, it can be used for SLA and KPI metrics and we are all aware of the fitment into curve for the year end appraisal. There are numerous benefits in we are able to plot and interpret the data.

With AI the link between data, data mapping, data interpretation and actions will be tied together. Don't just map and plot data, automate the process so that you can spend time on actions

There are some disadvantages on the use of Histogram - is that it will not be able to capture the time orderliness of the data set - which data point has occurred first, second and so on will not be evident in a histogram

Is Bar Chart similar to Histogram?

No, they are different. Although histograms and bar charts use a column-based display, they serve different purposes. A bar graph is used to compare discrete or categorical variables in a graphical format whereas a histogram depicts the frequency distribution of variables in a dataset

Interested and want to partner

To my connections, if any of you are interested to know more about the tools and techniques and wanted help in automation or have a business challenge which needs Quality Transformation. Reach out to me and I will be glad to support. I have partner friends who are excelling in the field of Training (Quality Related - Yellow, Green, Black and Lean Training) and in end to end business transformation

Soon we will be having couple of online sessions (1 hour each) to go thru what Quality Training can offer and what is it for you? Session is not free, it needs 60 minutes of your time as an investment

Please share your comments and suggestions

Thanks

DK