Gathering the Data
The first thing we need to do is enter all of the required data in Excel. In our example, we will look at a list of data that contains information on the number of defective products found in several manually inspected batches. The screenshot below shows a portion of this list. (Click any image for a larger view.)
Although we’ve applied some formatting to this list to make it look a little prettier, that’s not really necessary, especially if you don’t plan to use the list in any type of presentation or distribution.
After the raw data is entered, the next step is to decide how to group that data into sections or intervals. There are many ways to accomplish this task, some of which use more advanced statistical analysis that is beyond the scope of this article. However, since our data collection is rather small (only consisting of 64 items), we’re going to use that highly advanced mathematical method known as “eyeballing" and just make a rough guess as to how we should group the information.
A quick glance at the data in our list shows that the number of defects in each batch is always between 0 and 40. So, we’ll try grouping that data into intervals of length 5. That is, we’ll determine how many batches have 0-5 defects, how many have 6-10 defects, and so forth. This information is displayed in the table shown below.
Now that we have the data in order, the next step is to construct the histogram in Excel. We’ll continue with that in Part 2 of this series.