So, the above instructions are how to create a manual Histogram graph, which you must know and understand for the CQE Exam.īut who’s going to be creating a Histogram on paper now-a-days? So I wanted to include a YouTube video on how to create a Histogram in Excel 2010. Here’s another video from Khan that walks you through the creation of a Histogram. It’s a bit slow for my taste, but it walks you (slowly) through the entire process! Here’s a good YouTube video that explains the basic method of constructing a Histogram by hand. They put together an Interactive Histogram that shows you how a Histogram changes when you play with the Width or Interval of each Bin. Here’s a great resource from ASQ that will help you calculate the right number of Bins & the Width of each Bin for your Histogram. Resources & Videos for Histogram Creation Similar to selecting the right number of total Bins, it’s important that you keep all the Bin widths the same or this will skew the distribution of the data. Then you can divide your data Range (80), by the total number of Bins, lets say 8 in this instance. So for example, let’s say you’re creating a Histogram of Student’s Test Scores on an exam and the maximum score was 100 and the minimum score was 20 then your Range is 80(100 – 20). To do that you take the entire Range of the data (Max data point minus Min data point) and divide by the total number of Bins. Once you’ve determined the number of Bins for your Histogram, it’s time to calculate the Width or Range of each individual Bin. I also have to note that I’ve seen other people just take the Square Root of the total data size to get the number of Bins. Selecting the correct number of Bins is important as it can drastically affect the appearance of your data, which might lead you to the wrong conclusion.īelow is a table from The Quality Toolbox that you can reference when selecting the proper number of Bars.
The number of Bars for your Histogram will depend on the number of data points you collected. Now that you’ve collected an adequate amount of data, it’s time to calculate the number of Bars, sometimes called Bins or Ranges, for your data set. On the flip side of this requirement, one of the strengths of the Histogram is that it allows you to easily analyze large data sets, so don’t feel shy about collecting or analyzing ALOT of data. Without an adequate amount of data, you cannot make reasonable conclusions about your data.īasically you may miss the pattern in the variation. To accurately analyze a data set, it’s commonly recommended that you have at least 50 data points. So – you’ve got some data and you’d like to create a Histogram to study the pattern of variation – Great!īelow are the 3 steps you must go through to create a powerful Histogram. If your data is discrete or in Categories, then you should use a Bar chart instead of a Histogram. Yet there is a distinct difference between a Histogram and Bar Chart, and you need to know which one to use depending on the data analysis that you’re trying to perform.Ī Histogram will group your data into Bins or Ranges while a bar chart displays discrete data by categories. I said above that the Histogram is a type of Bar Chart because they both use vertical bins to display data. Difference between a Bar Chart & Histogram In that way, the pattern of the variation within the data will become obvious! More on Distributions below. Which means that every piece of data that you collect will have variation in it, and this variation will exist in a “Pattern”.Īnd the best way to see or understand this Pattern of variation is to graph your data using a Histogram. Why would you want to graphically display data?īecause as a Quality Engineer you probably already understand that every process, product or service has variation.
More specifically, a Histogram is a type of Bar Chart that graphs the frequency of occurrence of continuous data, and will aid you in analyzing your data. A Histogram is a Quality Control Tool that graphically displays a data set.
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