How to Make a Histogram

Histograms represent data by frequency of occurrence or percentage. They are similar to bar graphs, but the categories represented by bar graphs do not have to be in any particular order, whereas the data on histograms represent ordinal data, or data that does fall in a particular order. You can create histograms by hand or by using a program such as Excel.

Things You'll Need

• Raw data
• Graph paper
• Pencil
• Ruler
• Data analysis or spreadsheet software

Instructions

Draw a Histogram by Hand

1. Organize your data into a table. Create one column for data range categories, divided into equal intervals that will include all of your data (for example, 0-10, 11-20, 21-30), and another column for frequency or percentage.

2. Create a graph on graph paper. Mark the data range intervals on the x-axis (horizontal axis) with no space between the categories. Mark frequency or percentages on the y-axis (vertical axis), also in equal intervals.

3. Plot your data. For each data range category, draw a horizontal line at the appropriate frequency or percentage marker. Then, create a vertical bar for that category reaching up to the marked frequency or percent. Do this for each data range category.

Plot a Histogram Using Computer Software

1. Enter your data into a spreadsheet. Enter each data value into its own cell.

2. Enter the category values you wish to use.

3. Select the histogram tool from your software menu. Highlight the raw data values for "Input Range," or for plotting on the y-axis. Highlight the data range categories for the "Bin Range" or x-axis values.

4. Enter desired labels and select any other options you wish to include, such as cumulative percentages. Select the "Graph Output" option, then click "OK."

5. Adjust the size of the resulting graph by clicking and dragging the corners. You may export the table and graph created in the spreadsheet to other programs.

Tips & Warnings

• To calculate relative frequency, or percentages, divide the frequency of one particular data category by the total number of data collected. These percentages can be represented by a histogram or pie chart.

• Using a data analysis and spreadsheet program is very useful for large amounts of data. You don't have to enter the data in any specific order, and the software will calculate frequencies and percentages for you.

• Usually, you must select a graphing option from the software you are using. Otherwise, it may just create a table of your data.