A histogram is a bar graph that shows a distribution of values, with each bar representing a range of information, rather than just one piece. In order to find the mean, or average, of these pieces of information, you need to assign each group of data a number and find the average by adding them all together and dividing by the total. You can then go back to the list of assigned numbers and see which range correlates with the average number.

Count the number of pieces of information included in the histogram. This can be found by adding up all of the pieces of data that correlate with each bar.

Assign each range of information a number, going in numerical order. For example:

1 - 2 per cent: assign "1."

2 - 3 per cent: assign "2."

3 - 4 per cent: assign "3."

Add together the values of each piece of information, using the assigned numbers and the frequency, as shown by the vertical axis.

Divide the total value of the data by the number of pieces of data. This will give you the average.

Find the average range by rounding to the nearest whole number and looking at the assigned numbers. Using the example, if the final number is 2, you know the average range of the data on the histogram falls in the 2 - 3 per cent range.