How To Make A Histogram

There are a number of steps in constructing histograms for business management presentations. The first step is to learn the facts. Be as knowledgeable as possible about every aspect of the data you’re concerned with and the situation you wish to examine.

How many samples have to be measured to achieve the desired degree of accuracy? In other words, how large is the lot size, or population? In the example given earlier, the population is the number of bars of soap weighed. This number is often abbreviated with a capital N. Use random selection techniques to minimize the possibility of bias.

The next step is to measure each sample (in this case, the weight of each bar of soap). Determine the range by noting the heaviest and lightest bars. If the heaviest bar is 106.9 grams and the lightest is 100.1 grams, the difference, or range, is 6.8 grams.

Now you’re ready to begin constructing the histogram. How many columns should there be? As a rule of thumb, seven to 10 columns works fine. Either too few or too many can make the graph difficult to interpret:

Using 14 columns gives the histogram an erratic up-and-down look. In this example, because the range is almost seven, seven columns are presented. As you can see in the example below, averaging multiple columns of data sometimes smoothes out the curve, without hiding facts of any significance:

Order your sample data according to the measurement parameters you have selected. Use your data to construct the histogram, keeping the columns and their boundaries accurately proportioned and logically presented. When you’re done, you may want to include a legend at the bottom, a label that includes the name of the group, the date, where the data came from, and the size of the sample (which is often indicated with a small n).

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