Symmetric data should look nearly identical if folded in half at the center point of the distribution. The first distinguishing feature apparent in a histogram is the number of modes, or peaks, in the distribution. A peak occurs anywhere that the distribution falls and then rises again, even if it does not rise as high as the previous peak. A unimodal distribution only has one peak in the distribution, a bimodal distribution has two peaks, and a multimodal distribution has three or more peaks.Īnother way to describe the shape of histograms is by describing whether the data is skewed or symmetric. Histograms are useful for showing patterns within your data and getting an idea of the distribution of your variable at a glance. Using one versus the other is more a matter of taste than a required method. The same general shape of this distribution is seen in the two histograms using six bins and 12 bins. Using four bins does not provide nearly enough detail to interpret the distribution. In the images below, we used several different bin sizes to create histograms of the same sample data: To create bins, divide the heights up into evenly spaced ranges and record how many students fell in each range. The heights were measured in inches and ranged from 59 to 81 inches. Note: In Excel, you must create your own bin ranges, while in R and most other statistical analysis software, the bins will be automatically created for you (and modified as necessary).Įxample: You collected data on the heights of 100 high school students. Bins are created by dividing the range of responses in to an equal number of bins. The larger number of responses you have, the more bins you can use. The x-axis of a histogram reflects the range of values of a numeric variable, while the y-axis can reflect either the frequencies (counts) or relative frequencies (percentage of the total counts) for the range of values of your numeric variable.Ĭonventionally, it is best to have between 5 and 15 bins, depending on the number of different values that occur in your sample. Similar to a bar chart in which each unique response is recorded as a separate bar, histograms group numeric responses into bins and display the frequency of responses in each.

Histograms provide a way to visualize the distribution of a numeric variable.

Histograms in excel