What Is a Histogram?
Summary:
- Learn the answer to the question: What is a histogram? A histogram is a graph that shows how numeric data is distributed across value ranges by grouping values into bins.
- Histograms help reveal patterns such as whether data are symmetric, skewed, or clustered in certain ranges.
- Unpack the question: What is relative frequency? Relative frequency is the number of observations in a bin divided by the total number of data values.
- Learn how to read a histogram effectively in order to gain insights from the data. A rule of thumb is to start with the x-axis, then check the y-axis, shape, peaks, spread, and any gaps or outliers.
- Explore the basics of how to create a histogram in Excel using built-in tools.
What is a Histogram and Understanding Them
Histograms are powerful tools for exploring data patterns by displaying them in a familiar-looking graph. They look similar to bar charts, but they serve a different purpose. Unlike bar charts, histograms group numeric values into intervals to show frequency distribution. The histogram's name originates from the Greek roots histos, meaning "upright," and gramma, meaning “something written or drawn.”
To answer the question, what is a histogram, think of the following situations you're familiar with. Maybe your favorite restaurant has a chart that represents its busiest hours. Or a teacher wants to show her class how they scored on a recent test. These are situations where visualizing numeric data can help you understand patterns across a range, whether it's a range of times or test scores.
A histogram is a graph that shows how numeric data is distributed across value ranges. It takes a range (or interval) of values and groups them together in bins. Each bin is represented by a bar. The height of each bar shows the number of observations in that interval.
With a single view, you can see patterns in data, such as whether the data are symmetric or skewed. These insights can help you identify patterns, turning a series of raw numbers into something you can learn from. Histograms are a foundational concept in statistics — and one that students can explore in depth through the Outlier by Savvas Dual Enrollment Intro to Statistics course, which covers data visualization and distribution as part of a college-level curriculum accessible to high school students.
In the case of the restaurant, you might find that their lunch hours are by far the busiest, perhaps indicating that their lunch special is successfully bringing in customers. Alternatively, a histogram showing test scores might indicate that most students aced the exam, and that the teacher can challenge them with more advanced coursework.
What is Relative Frequency? Learn Their Relationship to Histograms
Before you learn how to read a histogram, you need to first answer: what is relative frequency? In a histogram, frequency is the count of observations in a bin. Relative frequency takes this count and divides it by the total number of data values. It shows the proportion or percentage of that value relative to the total dataset. Both can be highlighted on a histogram, depending on what insights you're trying to gain from it.
The x-axis shows numeric bins in order, while the y-axis shows frequency or relative frequency. Each bar on a histogram represents a bin. The taller the bar, the more observations fall within that bin or range.
Tips for How to Read a Histogram
You might naturally wonder how to read a histogram when you come across one. Here are some practical tips to help you understand what you're looking at:
- Start with the x-axis. This shows the data ranges for each bin, so you know what values each bar represents.
- Check the y-axis. This tells you how many values, or the relative frequency, fall in each bin.
- Look for the shape. A symmetric histogram suggests the data are evenly distributed around the center. A graph that appears skewed shows that the data are concentrated more on one side.
- Find the peaks. The tallest bars show where the data is concentrated most heavily.
- Notice the spread. A wide histogram means there's more variability. Meanwhile, a narrow one means values are clustered more closely together. Spread affects what you can learn about the data by glancing at the graph.
- Watch for gaps and outliers. Empty spaces or isolated bars are a sign of unusual values or separate groups. Consider what this means for the information your chart represents.
If you're wondering how to read a histogram, consider where most of the data falls and how it spreads across bins. Think about what its shape says about the information it represents.
How to Create a Histogram in Excel
Are you wondering how to create a histogram in Microsoft® Excel®? Here's a step-by-step process to make and configure a histogram:
- Collect your numeric data and add it to a column in Excel.
- Select Insert > Insert Statistic Chart > Histogram. This generates the graph, but you still need to configure the bins.
- Right-click the horizontal axis of the chart, select Format Axis, and select Axis options.
- Set the number of bins and the bin width.
Choosing the right bin size can be tricky. Too few bins can hide structure, while too many can make it harder for a viewer to gain insights from looking at the graph. You might need to experiment with some bin widths to achieve the right result. It often helps to use rules of thumb such as the square-root rule, Sturges’ rule, or the Freedman–Diaconis rule.
Practical tools make it easier to create a histogram in Excel. Built-in chart options or the Data Analysis Toolpak help you define bin ranges and display counts, relative frequencies, or percentages.
Do you want to learn more about creating and leveraging histograms? We explore how to create a histogram in Excel, how to find the mean of a histogram, and other key statistics concepts in the Outlier by Savvas Intro to Statistics course.
Intro to Statistics – Outlier by Savvas Dual Enrollment Course
You Might Also Like
College Algebra – Outlier by Savvas Dual Enrollment Course
Help lead students to their math “aha” moments with unexpected real-world examples all while earning transferable college credits in this 100% online dual enrollment course.
Intro to Macroeconomics – Outlier by Savvas Dual Enrollment Course
Teach students about how the economy shapes every aspect of our modern world: from the international order to political systems… even future interplanetary economics in this 100% online dual enrollment course.