Box Plots in Psychology Research: Definition, Interpretation, How They're Used

Table of ContentsView AllTable of ContentsWhat They MeanWhy They’re HelpfulHow to Interpret a Box Plot

Table of ContentsView All

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Table of Contents

What They Mean

Why They’re Helpful

How to Interpret a Box Plot

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A box plot, also known as a whisker plot, is a visual representation that displays the distribution of a data set along with severalkey statistical measures. It provides a graphic summary of important information about a set of data, including the minimum score, first quartile, median, third quartile, and maximum values.

The box plot looks like a rectangle, often called the box, which indicates the interquartile range. The box center represents the median, and the outer sides of the box represent the first quartile (25th percentile) and third quartile (75th percentile), respectively. The “whiskers” extending from the box show the range of data, excluding the outliers.

This article discusses what a box plot can tell you about a data set and the different parts of a box plot. It also covers how box plots can help you analyze data and how to interpret one.

What Information Do Box Plots Tell You?

A box plot provides a number of key points of data that can help reveal important details and information about the data they describe.

Some of these key points include the median, the interquartile range, and the minimum and maximum values excluding the outliers.

The 7 Elements of a Box Plot

The seven key elements of a box plot are:

Box plots are non-parametric, meaning they do not make assumptions about the underlying distribution of the data. Instead, they function to give a visual representation based on the median and quartiles.

Box Plot OrientationBox plots can be presented horizontally and vertically. They are often presented vertically inprofessional academic papers.

Box Plot Orientation

Box plots can be presented horizontally and vertically. They are often presented vertically inprofessional academic papers.

Why Are Box Plots Helpful in Analyzing Data?

Box plots have a number of important uses and benefits in conveying and analyzing data inpsychology research.

These graphic representations can quickly convey important information about the spread and symmetry of a distribution. Using these tools, it is possible to create visual comparisons of different groups of data.

Researchers also suggest that box plots can help people improve their ability to interpret and understand complex information. This allows people to reason more effectively aboutquantitative information.

Box plots can also be a good alternative to histograms. While for a histogram it is generally recommended that you have a minimum sample size of 50 data points, a box plot can be effective with asample sizeof only five.Box plots can also be adapted in various ways to help improve comparison and interpretation. For example, a notch can be added to the box to show the 95% confidence interval for the median.

When interpreting data in a box plot, researchers typically follow a set of steps or methods to gain insights and draw conclusions. Here are the common steps used to interpret data in a box plot:

Look at Key Characteristics of the Data

The first step when interpreting a box plot is to look at some of the most important characteristics of the data:

Look for Signs of Unusual Data

It can also be helpful to look for signs that your data might be skewed or unusual in some way.

Make Comparisons

That does not mean that box plots are always the best choice for presenting data. They can be helpful for comparing groups, but a more detailed visual representation, such as ahistogram, can be more informative if you are looking at a single data set.

50+ Research Topics for Psychology Papers

5 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tukey JW.Exploratory Data Analysis. Addison-Wesley Pub. Co; 1977.Park JH, Lee DK, Kang H, et al.The principles of presenting statistical results using figures.Korean J Anesthesiol. 2022;75(2):139-150. doi:10.4097/kja.21508)Williamson DF.The box plot: a simple visual method to interpret data.Ann Intern Med. 1989;110(11):916. doi:10.7326/0003-4819-110-11-916Krzywinski M, Altman N.Visualizing samples with box plots.Nat Methods. 2014;11(2):119-120. doi:10.1038/nmeth.2813Hu K.Become competent within one day in generating boxplots and violin plots for a novice without prior R experience.Methods Protoc. 2020;3(4):64. doi:10.3390/mps3040064

5 Sources

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Tukey JW.Exploratory Data Analysis. Addison-Wesley Pub. Co; 1977.Park JH, Lee DK, Kang H, et al.The principles of presenting statistical results using figures.Korean J Anesthesiol. 2022;75(2):139-150. doi:10.4097/kja.21508)Williamson DF.The box plot: a simple visual method to interpret data.Ann Intern Med. 1989;110(11):916. doi:10.7326/0003-4819-110-11-916Krzywinski M, Altman N.Visualizing samples with box plots.Nat Methods. 2014;11(2):119-120. doi:10.1038/nmeth.2813Hu K.Become competent within one day in generating boxplots and violin plots for a novice without prior R experience.Methods Protoc. 2020;3(4):64. doi:10.3390/mps3040064

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Tukey JW.Exploratory Data Analysis. Addison-Wesley Pub. Co; 1977.Park JH, Lee DK, Kang H, et al.The principles of presenting statistical results using figures.Korean J Anesthesiol. 2022;75(2):139-150. doi:10.4097/kja.21508)Williamson DF.The box plot: a simple visual method to interpret data.Ann Intern Med. 1989;110(11):916. doi:10.7326/0003-4819-110-11-916Krzywinski M, Altman N.Visualizing samples with box plots.Nat Methods. 2014;11(2):119-120. doi:10.1038/nmeth.2813Hu K.Become competent within one day in generating boxplots and violin plots for a novice without prior R experience.Methods Protoc. 2020;3(4):64. doi:10.3390/mps3040064

Tukey JW.Exploratory Data Analysis. Addison-Wesley Pub. Co; 1977.

Park JH, Lee DK, Kang H, et al.The principles of presenting statistical results using figures.Korean J Anesthesiol. 2022;75(2):139-150. doi:10.4097/kja.21508)

Williamson DF.The box plot: a simple visual method to interpret data.Ann Intern Med. 1989;110(11):916. doi:10.7326/0003-4819-110-11-916

Krzywinski M, Altman N.Visualizing samples with box plots.Nat Methods. 2014;11(2):119-120. doi:10.1038/nmeth.2813

Hu K.Become competent within one day in generating boxplots and violin plots for a novice without prior R experience.Methods Protoc. 2020;3(4):64. doi:10.3390/mps3040064

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