What Is a Histogram and Why Consider Creating One?

By Indeed Editorial Team

Published November 30, 2021

Visualizations can effectively describe a project's success and help stakeholders understand data sets. While you can create various graphs and charts to show progress, histograms are popular for summarizing data in the workplace. Understanding what a histogram is and when to use one can improve your effective communication skills. In this article, we answer the question, "What is a histogram?", list important histogram parts, describe how to create a histogram, present common histogram shapes, and discuss frequently asked histogram questions and helpful answers.

What is a histogram?

To answer the question, "What is a histogram?" it helps to understand that it's a graphing tool for summarizing discrete or continuous data measured in intervals. A histogram organizes data points into specified groups for others to understand. For each group, you construct a bar with a length representing the number of observations. For example, suppose you collect data on employment status. If 50 individuals started their job search this year, the bar representing zero to one year would be 50 units long. You can create a histogram when performing the following:

  • analyzing whether a process meets customer requirements

  • determining the difference between process outputs

  • analyzing the output from a supplier's process

  • determining whether a process changed over time

  • reporting data sets and making decisions based on current data

Parts of a histogram

Aside from the bars, here are other essential elements to include in a histogram:

  • A title: describes the information included in the histogram. It typically appears above or below the histogram to improve the graph's readability.

  • X-axis: shows the range of observations in the data set. Its unit varies depending on the unit

  • Y-axis: shows each group's frequency, which is the number of times it occurs

How to create a histogram

Follow these steps to create a histogram on a board or paper:

1. Obtain a histogram worksheet

A histogram worksheet is a grid for drawing histograms. Using one helps you create bars of equal width and improve your visualization's look. You can find these templates online and create several copies if you draw multiple histograms at work.

2. Draw and label the axes

While the X-axis is typically horizontal, the Y-axis is often vertical. Labelling the axes involves describing what each represents and including the units. It also involves determining the spacing for each bar. The X and Y axes typically meet at 0.

3. Create bars for each group

Draw the bars and ensure there are no spaces between them. You can highlight each bar's length to make them clearer on the histogram worksheet. If possible, use different colours to emphasize the bars.

Tips for creating histograms using software

Here are the best practices for creating histograms using computer applications:

Choose a suitable software application

Various software programs have functionalities for creating histograms. For example, Microsoft Excel can help you automatically design one. Evaluate the features each software application provides and assess whether they're easy to use. You may download the computer application on your computer system or create your histogram online.

Related: Advanced Excel Skills: Definitions and Examples

Customize the histogram

Regardless of the software program you choose, customizing a histogram can make it more appealing to its recipient. For example, you may change text labels or chart styles. Many software applications also allow you to filter the histogram, especially if it visualizes a large data set. Ensure the customization effects you use complement the histogram.

Related: The Best Computer Skills to Develop for Work

7 histogram shapes and their meanings

After drawing a histogram, it may have various shapes, such as:

1. Normal distribution

Histograms can have a bell-shaped look, which means data points symmetrically occur on both sides of a central point, called the mean. In normal distributions, the central point is also the middle value of the data set, called the median. It can help to trace a curve at each bar's middle to see whether your data has a normal distribution.

2. Skewed distribution

A skewed distribution is asymmetrical, which means data points are unevenly on both sides of the mean. For example, suppose you're analyzing a metal sample's purity. You can expect a skewed histogram because metals typically can't be over 100% pure. Similarly, you may have a skewed histogram if you're analyzing holes that cannot be smaller than a drilling bit or call durations that aren't typically less than zero minutes.

3. Bimodal distribution

A bimodal distribution has two peak points. If your histogram has this look, it typically indicates that your data set has two distinct groups. For example, a bimodal distribution of school grades may show several students had As and Bs. Similarly, a data set from two shifts might be bimodal, with each peak representing the highest frequency during a shift.

4. Multimodal distribution

Similar to bimodal distributions, a multimodal distribution has multiple peaks. Histograms often have this look if you combine several processes in your data set. For example, suppose you collect the ages of college or university students. If many participants are 18, 19, or 20 years, the histogram you create might have a multimodal distribution.

5. Edge peak distribution

Histograms with an edge peak distribution look like those with normal distributions. The difference is that edge peak distributions have a side peak, aside from the central one. This peak may be an outlier in the data set. For example, suppose you ask employees to grade their satisfaction levels on a scale of one to 10. If several employers respond with 11, you can expect an edge peak distribution when creating the histogram.

6. Comb distribution

In a comb distribution, bars are alternatively long and short. You can expect histograms with this shape if you approximate data points. For example, suppose you're working with temperate data. If you approximate the values to the nearest 0.2 degrees and each bar has a width of 0.1 degrees, you might get a comb distribution.

7. Truncated distribution

This distribution looks like a normal distribution with fewer data point variations. You can typically obtain this shape by first creating a normal distribution and focusing on a range around the central point. For example, if your histogram has a normal distribution and shows data between one and nine, focusing on data points between four and six typically creates a truncated distribution.

FAQs about histograms

Here are helpful answers to common questions about creating histograms:

What is the difference between a histogram and a bar chart?

Here are ways to differentiate histograms from bar charts:

  • Usage: While histograms show a variable's distribution, bar charts are visual tools for comparing data categories.

  • Variable type: Histograms typically use numeric variables. In comparison, bar charts use categorical variables.

  • Rendering: Creating a histogram requires you to group data points and ensure there are no overlapping intervals. In comparison, each data point in a bar chart is a separate bar.

  • Space between bars: While you can have spaces between the bars you draw in bar charts, histograms have no spaces.

  • Arrangement: You can typically reorder the bars in a bar chart, unlike in histograms.

What measures can you find from a histogram?

You can find a data set's mean, median, and mode from a histogram. These analyses provide estimates, and an effective way to determine statistical measures is often to assume the data within each class is uniform. You often use each bar's length for calculating the mean, median, and mode. For example, the class that has the highest bar length is the data set's mode.

What roles typically require you to create histograms?

Here are common positions that involve creating histograms:

  • Mathematician: studies math principles and develop theories and ideas

  • Quantitative analyst: applies mathematical and statistical methods to finance and risk management. They help companies make informed business and financial decisions.

  • Data analyst: collects, evaluates, and interprets data sets to answer a question or solve a business challenge

  • Teacher: educates students in schools, colleges, universities, and training institutes

  • Researcher: locates answers to questions or solve challenges by observing situations, developing theories, conducting experiments, and presenting their findings

  • Technical writer: creates technical documents, such as instruction manuals, journal articles, and product reviews. They often create diagrams to show how a product or service works.

  • Marketer: promotes a company's products or services to a target audience.

Related: What Are Jobs for Visual Learners? (Salaries and Duties)

Can a histogram be horizontal?

A histogram can be vertical or horizontal, depending on the worksheet you use and the drawing space available. Horizontal histograms can make it easier to read each class's frequency. To change a histogram from its vertical orientation to become horizontal, switch the X and Y axes on your worksheet.

Please note that none of the companies mentioned in this article are affiliated with Indeed.

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