How to Do a Box and Whisker Plot Easy

How to Identify Box Plot Outliers? Easy Steps

A Box Plot is the visualization design we recommend if your goal is to display quartiles, mean, and outliers attributes in data.

So, what is an outlier?

An outlier is a value that lies in the extremes of a data series and thus can affect the overall observation. Outliers are also termed asextremes because they lie on either end of a data.

A Box Plot Outliers detector (Box and Whisker Graph) is easy to interpret, even for non-technical audiences.

Excel lacks Box Plot Charts. And this means you've got to use other pricey tools or plot the chart manually. So, if your goal is to display high-level insights, you've got to think beyond Excel.

We're not recommending you do away with Excel, especially if your goal is to access ready-made and visually appealing Box Plots.

Download and install a particular add-in (which we'll mention later) into your Excel to access the ready-to-go Box Plot Outliers detector.

In this blog, you'll learn:

• How to get started with the Box Plot Outliers?
• How to use a Box Plot Diagram to Identify Outliers?
• Also, we address the following questions:
  • What is a Box Plot?
  • What is the 1.5 IQR rule?
• Also, we'll recommend the best add-in to install in your Excel to access visually stunning and easy-to-interpret Box Plot Outliers Chart.

How to Identify Box Plot Outliers? Easy-to-Follow Steps

Before addressing the how-to guide, let's address the following question: what is a Box Plot?

What is a Box Plot?

A Box Plot is a visualization design that uses box shapes to display insights into data.

The chart simplifies bulky and complex data sets into quartiles and averages. Also, you can use the chart to pinpoint outliers in your data. The Box Plot segments key variables in quarters or (quartiles).

For instance, you can draw boxes to connect the first quartile to the third quartile. In this case, the boxes will represent the average values of key data points.

Whiskers are lines that identify numbers outside of the average data points.

The chart displays your data's shape, variability, and center (or median) information. Also, you can leverage the chart to determine the skewness of data points.

Essentially, a Box and Whisker Chart shows the following points of data:

• Minimum range
• Lower quartile
• Median
• Upper quartile
• Maximum range

Besides the five summary numbers, the visualization displays the following:

• Minimum score
• Median
• Maximum Score
• Lower Quartile
• Upper Quartile

Let's check out the elements in detail.

The minimum score is the lowest score, excluding outliers (shown at the end of the left whisker).

Lower Quartile: 25% of all variables fall below the lower quartile value.

The median is the mid-point of the data and is shown by the line that divides the box into two parts (sometimes known as the second quartile). Half the scores are greater than or equal to this value, and half are less.

The upper quartile is 75% of all variables that fall below the upper quartile value (also known as the third quartile). Thus, 25% of data points are above the value.

The maximum score is the highest score, excluding outliers (shown at the end of the right whisker).

Whiskers: The upper and lower whiskers represent scores outside the middle 50% (i.e., the lower 25% of scores and the upper 25% of scores).

The interquartile range (IQR) ranges between the 25th and 75th percentile).

A Box and Whisker Graph can help you to visualize large datasets. More so you can easily detect the symmetry of the data at a glance by using the chart. Unlike other data visualization techniques, the Box Plot displays outliers.

The visualization design is best-suited for comparing distributions between key groups in data. The charts are compact in design to help you display a ton of information without clutter.

Data sets can sometimes contain outliers that are suspected to be anomalies (perhaps because of data collection errors or just plain old flukes).

If outliers are present, the whisker on the appropriate side is drawn to 1.5 * IQR rather than the data minimum or the data maximum. Small circles or unfilled dots are drawn on the chart to indicate where suspected outliers lie.  On the other hand, filled circles are used for known outliers.

Keep reading because we'll show you how to spot Box Plot Outliers in the coming sections.

What are Box Plot Outliers?

An outlier is a value that lies in both extremes of data. In other words, it's a value that lies outside the overall distribution pattern and thus can affect the overall data series.

These anomalies are treated as abnormal values that can distort the final insights.

Data visualization experts agree that a value should be regarded as an outlier if it's 1.5 times bigger or smaller than the expected observation.

In the coming section, we'll address the following question: what is the 1.5 IQR rule?

What is the 1.5 IQR Rule?

To understand the 1.5 IQR rule, we'll cover the interquartile range, abbreviated as the IQR.

The interquartile range is just the width of the box in the chart.

In other words, IQR = Q3 – Q1.

The IQR measures how key data points are spread out. Therefore, an outlier is 1.5 multiplied by the IQR value of your data.

Keep reading to discover how to use Box Plot Diagram to identify outliers. You don't want to miss this.

How to Calculate Box Plot Values?

Box and Whisker Plot show the distribution of key data points along a number line.

You can generate the chart by ordering a data set to find the median, upper and lower quartiles, and upper and lower extremes.

To calculate values, such as mean, follow the steps below:

• Order the data from least to greatest.
• Find the median or middle value that splits the data set into two equal groups. If there is no middle value, use the average of the two middle values as the median.
• Find the median for the lower half of the data set.
• Find the median for the upper half of the data set.
• Use these five values to construct a Box Plot displaying the following: lower extreme, lower quartile, median, upper quartile, upper extreme.
• Draw vertical lines through the lower quartile, median, and upper quartile.
• Form a box by connecting the vertical lines from the lower quartile, median, and upper quartile.
• Plot the whiskers from the extremes of the box.

Keep reading to learn how to identify Box Plot Outliers effortlessly. Also, you'll discover how to use Box Plot Diagram to identify outliers.

You don't want to miss this.

How to Create the Chart using Box Plot Outliers Generator?

Excel is one of the go-to data visualization tools for businesses and professionals.

However, this freemium spreadsheet tool does not natively support Box Plot Outliers Diagram. In other words, you'll never find this visualization design in Excel.

Well, you don't have to do away with the spreadsheet app.

You can turn Excel into a reliable data visualization tool loaded with ready-made and visually stunning Box and Whisker Charts by installing third-party apps, such as ChartExpo.

How to read a Box Plot in Excel should never be a stressful task. Keep reading to learn more.

Why ChartExpo?

ChartExpo is an add-in you can easily install in your Excel.

With 50+ advanced visualizations, ChartExpo turns your complex, raw data intocompelling, easy-to-decode, visual renderings that tell the story of your data.

The application produces simple, ready-to-go, and clear visualization designs with just a few clicks.

Yes, ChartExpo generates ready-made Box Plots that are amazingly easy to interpret, even for non-technical audiences.

In the coming section, you'll get to see ChartExpo in action. You don't want to miss this.

Example

This section will use the Box Plot Outliers generator (ChartExpo add-in) to visualize the data below.

Gender	Age
Male	29
Male	34
Male	37
Male	28
Male	45
Male	55
Male	36
Male	28
Male	43
Male	35
Male	45
Male	34
Male	31
Male	32
Male	34
Male	30
Male	36
Male	42
Male	32
Male	48
Male	48
Male	27
Male	31
Male	24
Male	78
Female	22
Female	38
Female	40
Female	25
Female	23
Female	36
Female	37
Female	49
Female	44
Female	26
Female	41
Female	30
Female	38
Female	45
Female	40
Female	25
Female	38
Female	26
Female	44
Female	39
Female	43
Female	44
Female	48
Female	31
Female	33
Female	38
Female	37
Female	38
Female	43
Female	67
Female	76
Female	80

Click here to install ChartExpo into your Excel. Once you're done, follow the easy steps below.

• Open your Excel and paste the table above.
• Open the worksheet and click theInsert Menu button.
• Click the My Apps button and then click theSee All, as shown below.

• Click theInsert button to get started with ChartExpo.
• Click the Search Box and type "Box and Whisker Chart."

• Once the Chart pops up, click on its icon to get started, as shown above.

• Select the sheet holding your data and click the Create Chart from Selection.

• Check out the final Box Plot outlier Chart below.

Insights

• The ages between 68 and 85 years were outliers.
• The maximum and minimum ages among the males were 26 and 57 years, respectively.
• The maximum and minimum ages among the females were 20 and 48 years, respectively.
• The median age of male respondents is 39 years. Conversely, the median age of females is 42 years.

Advantages of Box Plot Outliers:

Check out the benefits of the chart below:

• A Box and Whisker Graph can help you to visualize large datasets.
• You can easily detect the symmetry of the data at a glance by using the chart.
• Unlike other data visualization techniques, the Box Plot displays outliers.

FAQs:

Why is 1.5 IQR equal to Box Plot outlier?

John Tukey was the first person to use Box Plot outliers to display insights into data. He came up with the 1.5 IQR requirement to pinpoint outliers.

The IQR measures how key data points are spread out. Therefore, an outlier is 1.5 multiplied by the IQR value of your data.

What causes an outlier?

An outlier is a value that lies in both extremes of data.

In other words, it's a value that lies outside the overall distribution pattern and thus can affect the overall data series.

Outliers are caused by the following:

• System behavior
• Fraudulent behavior
• Human and instrument errors

Wrap Up

As we said, a Box Plot is the visualization design we recommend if your goal is to display quartiles, mean, and outliers attributes in data.

So, what is an outlier?

Outlier is a value that lies in the extremes of a data series and thus can affect the overall observation. Outliers are also termed asextremes because they lie on either end of a data.

A Box Plot Outliers detector (Box and Whisker Graph) is easy to interpret, even for non-technical audiences.

Excel lacks Box Plots.

The only viable options are using other pricey data visualization tools or plotting the chart manually.

Think beyond the spreadsheet application if you intend to display attributes, such as mean, outliers, and quartiles in your data.

So, what's the solution?

We recommend installing third-party apps, such as ChartExpo, into your Excel to access ready-made Box and Whisker Charts.

ChartExpo is an add-in you can easily download and install in your Excel app. Besides, this tool comes loaded with insightful and easy-to-interpret Box Plots. You don't need programming skills to visualize your data using ChartExpo.

How to use a Box Plot Diagram to identify outliers should never stress you.

Sign up for a 7-day free trial today to access easy-to-interpret and ready-made Box and Whisker Charts.

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Source: https://chartexpo.com/blog/box-plot-outliers

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