Tableau Control Chart Explained (Detailed Guide with Examples)

A control chart is an important tool for data analysis that monitors performance and detects changes in a process. It helps us understand whether a process is stable or shows unusual variations.

In Tableau, creating a control chart is simple, but understanding its underlying concept is very important. Many beginners only learn the steps but do not understand how it works.

I was working with the sales team to analyze product sales performance over the past 5 years. In this analysis, we need to identify unusual sales patterns, such as sudden spikes and periods of low sales.

To highlight the highs and lows in the Sales data, we need to create a Tableau visualization. In this, we can see both the usual sales and those that fall outside the usual range.

For this Tableau data visualization, I used the Tableau Control Chart. In this chart, I showed which years’ sales were outside the normal sales range, highlighting high and low sales relative to expected performance.

In this Tableau tutorial, I will explain the Control chart in Tableau and how to use it to identify variations in data values.

Table of Contents

What is a Control Chart in Tableau?

A control chart is a graphical representation used to study how a process changes over time.

It shows:

Data points (over time)
Average line (mean)
Upper Control Limit (UCL)
Lower Control Limit (LCL)

In Tableau, a control chart shows how a value, such as sales, profit, or delivery time, changes over time and whether it stays within a normal range.

It has two limit lines (upper and lower) that show the usual range of variation. If the data points remain between the limits, the process, like sales, is normal.

If some points exceed or fall below the limits, it indicates that something unusual is happening, such as sales much below average.

This makes control charts useful for tracking performance, spotting problems, and improving processes.

Why Use Control Charts?

Control charts are used for:

Monitoring performance
- Track whether your process is working properly
Identifying issues
- Detect sudden spikes or drops
Improving quality
- Used in quality management and analytics
Decision making
- Helps in taking data-driven decisions

Key Components of Control Chart in Tableau

Data Points
- These are actual values plotted over time
Mean (Average Line)
- The center line showing average performance
Upper Control Limit (UCL)
- Maximum acceptable limit
Lower Control Limit (LCL)
- Minimum acceptable limit

Advantages of Control Charts

Easy to understand
Helps detect problems early
Improves process stability
Useful for business analytics

Create a Control Chart in Tableau

To create a control chart in Tableau, we will use Tableau’s Superstore data. Now, connect Tableau with the data source and follow the steps below.

In the Tableau sheet, add the Sales(Sum) to the Rows and Date Order to the Columns. By default, the date is in year format. Here, set it to Month (continuous).

With this, we will create a line chart to use in our control chart.

For a control chart, we need upper and lower bounds to show deviations. We also want to give users an option to widen the gap between upper and lower bounds. For this, we will create a parameter.

To create a parameter, click on the dropdown in the data bar and select Parameters. Then enter the name of the parameter and select range Minimum as 1, Maximum as 3, and Step size as 1.

To show the upper and lower bounds, create the formula fields using the formulas below.

//Lower Bound
WINDOW_AVG(SUM([Sales]))-(WINDOW_STDEV(SUM([Sales]))* [N number of Standard deviation])

// Upper Bound
WINDOW_AVG(SUM([Sales]))+(WINDOW_STDEV(SUM([Sales]))* [N number of Standard deviation])

To show the Upper and Lower bounds in the chart, we will use the reference lines. For this, drag the calculated fields Upper bound and Lower bound to the Details card in the Marks section.

After this, click on the Sales axis and select Add reference line. In the reference line, select the value as Lower bound to show the lowest range.

In the Formatting section, select the line pattern, thickness, and color density. After this, click OK.

To show the upper bound or upper range, click the Sales axis and select Add reference line. In this reference line, select the Value as the Upper bound.

In the Formatting section, select the reference line’s pattern, thickness, and color, then click OK.

Show Range lines in Tableau Control Chart

Now, we can see the reference line of the upper and lower bonds. The sales between these two lines will be the usual sales.

To display sales outside the regular range, we will use a circle chart to display the data points. For this duplicate Sales(SUM) on the Rows and select the second chart type as Circle.

Create Control Chart using Lines in Tableau

To show these circle data points on the line chart, click on the Sales (SUM) 2 in the Rows and select Dual Axis.

With this, we can see that the data points fall outside the usual upper and lower bounds.

To show the outlier data values in a different color, we need to create a formula field.

//Color Outliers
SUM([Sales])>[Upper Bound]
OR 
SUM([Sales])<[Lower Bound]

If you want to show different colors for upper and lower values, then you can create separate formula fields as:

//Color Upper Outliers
SUM([Sales])>[Upper Bound]

//Color Lower Outliers
SUM([Sales])<[Lower Bound]

Now, add the calculated field to the Color card in the Marks section of the circle chart.

With this, we can see the sales values outside the upper and lower bounds in a different color.

At last, add the Sales(SUM) to the Label card in the circle chart. This will display the sales figures for a specific month on the control chart data points.

With this chart, we can identify the outlier values in the sales figures. In this control chart, we can see the sales figures for specific months and whether they fall within or outside the usual sales range.

This way, we can create a Control Chart in Tableau to identify and highlight unusual sales patterns, such as sudden spikes and low sales.

Frequently Asked Questions

Q1: What is a control chart in Tableau?

It is a chart used to monitor data variation over time.

Q2: Does Tableau have a built-in control chart?

No direct option, but you can create using reference lines.

Q3: What are UCL and LCL?

Upper and lower limits are used to detect abnormal values.

Q4: Why is a control chart important?

It helps identify problems early and improve performance.

Conclusion

Control charts are powerful tools for analyzing data and improving processes. In Tableau, you can easily create control charts using line charts and reference lines.

In this Tableau tutorial, we have learned about the Tableau Control chart. In the above steps, we created a control chart by defining parameters and a reference line to indicate the upper and lower control limits.

We also displayed the outlier values in the Control chart in a different color to easily identify values that exceed the reference range in the Tableau Control Chart.