Fundamentals of Social Statistics by Adam J. McKee

A histogram is a graph that has vertical bars indicating the frequency, rate, or percentage of different categories or points along a continuous variable.  By convention, the frequency is placed along the vertical edge of the graph, and the category is placed along the horizontal line at the bottom.  You can use a histogram with either quantitative or qualitative data. The basic idea is to show how a variable is distributed among different categories.  The mode of a histogram is the most frequently occurring score.  A distribution of scores with two such high points is referred to as bimodal.

A histogram is akin to a bar graph in appearance, but there are fundamental differences in their application and the type of data they represent. Histograms illustrate the distribution of continuous data with adjacent bars, emphasizing the uninterrupted nature of the data. Conversely, bar graphs represent discrete data with discernible spaces between bars. A term often associated with histograms is “bin,” which refers to the range of values divided into a series of intervals. Essentially, bins group data points into categories, and the width of these bins determines the level of detail displayed in the histogram.

Why Use Histograms?

The intuitive design of histograms makes them highly effective for visual data interpretation. At a glance, one can discern which data categories or intervals (bins) have higher frequencies. Especially when dealing with voluminous datasets, histograms offer a succinct overview, streamlining the process of data comparison. Beyond mere frequency representation, histograms can unveil data distribution patterns like skewness—a measure of the asymmetry of the probability distribution. If a histogram leans to the right, it indicates positive skewness (few larger values), whereas a lean to the left signifies negative skewness (few smaller values). These distribution shapes are pivotal for analysts, offering insights critical for subsequent statistical endeavors.

Insights from Histograms

Histograms, with their visually arresting bar-like structures, offer a profound look into the nuances of data distribution. At their core, they reveal two essential facets of data: the central tendency and the variability. The central tendency is a measure that indicates the central or typical value for a dataset, and in a histogram, it’s depicted by where most of the data seems to concentrate. When the majority of the bars in a histogram cluster around a particular point, it suggests a pronounced central tendency, indicating that most of the data values hover around that central region.

On the other hand, the spread or dispersion of these bars provides a clear picture of the data’s variability. A wider distribution of bars stretching across the histogram denotes a higher degree of variability, suggesting that data values are spread out over a range. Conversely, when bars are densely packed and concentrated in a narrow region, it signals limited variability, indicating that most data points are similar and cluster around a common value. Through this visual representation, histograms effectively translate intricate numerical data into a format that’s easy to understand, making them invaluable tools for data analysts and researchers.

Potential Limitations

Despite their utility, histograms come with certain challenges. One significant consideration is the selection of appropriate bin width. An unsuitably high number of bins can clutter the visualization, making the data appear scattered and indecipherable. Conversely, very few bins might oversimplify the data representation, masking crucial details. Thus, for an accurate representation in a histogram, it’s paramount to find the right balance in bin width.


Histograms are graphical representations using vertical bars to denote the frequency or percentage of categories on a continuous variable. Positioned with frequency on the vertical axis and categories on the horizontal, they can handle both quantitative and qualitative data, revealing the distribution of a variable among categories. Their distinguishing feature is the mode or the highest frequency. When two such modes are evident, the distribution is termed “bimodal.” While similar to bar graphs, histograms are unique as they chart continuous data with adjoining bars. An important term in histograms is “bin”, representing intervals that group data points. Their intuitive design facilitates easy data interpretation, highlighting the central tendency and variability. Yet, choosing the right bin width is crucial to avoid oversimplification or overcomplication. In essence, histograms are a powerful tool for data visualization, but their accuracy hinges on careful construction.

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Last Modified:  09/25/2023

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