Histograms of 139 vocabulary scores with different sizes of class intervals and different numbers of intervals.

With interval size of 7, there are 13 intervals. This shows the shape of the distribution pretty well.

With interval size of 14, there are only 7 intervals. The details of the shape are less apparent.

With interval size of 28 there are only 4 intervals. The shape is barely apparent.

With interval size of 3.5, there are a lot of intervals. Now there is a little too much detail.

With interval size of 1.75, there is a huge number of intervals. The shape is so detailed that the details are really meaningless.