Visualizing Variability in Your Data Just Got a Little Easier in Minitab 19: Check Out the Improved Multi-Vari Chart

Jenn Atlas 02 October, 2019

Multi-Vari chart of Average Flavor by Product, Day

Good data analysis allows you to make smarter decisions faster. Here at Minitab, we are constantly striving to make it easier for you to analyze data and communicate those results so you can keep your projects moving forward. Case in point: the improved Multi-Vari Chart in the latest update to Minitab 19 (19.2.0).

The Multi-Vari Chart makes it easy to identify sources of variability in your data; whether you are using it as a preliminary analysis tool or in a final report to demonstrate the primary sources of variation. 


30-day Free Trial: Ready to try the new and improved Multi-Vari Charts in Minitab 19? Download the trial here


Example 1: Communicating the Results of a Clinical Study

Consider a clinical study where food manufacturers investigated flavor differences across six products. The study was repeated on Day 2. Here is a sample showing how the data are arranged:

Data from a clinical study where food manufacturers investigated flavor differences across six products.

We start by selecting the Multi-Vari Chart under Stat > Quality Tools > Multi-Vari Chart

The dialog for a Multi-Vari Chart is shown when you select Stat > Quality Tools > Multi-Vari Chart

The vertical axis represents the flavor score and the horizontal axis contains both the product codes and days.

Multi-Vari chart of Average Flavor by Product, Day

It’s easy to see that the average flavor scores, connected by the lines, are higher for LHA .50% w/ DRN 4 product across both days. Additionally, the Multi-Vari Chart makes it easy to see that the variation in flavor scores for the Current product was much smaller compared to all others.

If the goal is to maximize flavor, one reasonable conclusion is that while the Current product delivers a more consistent flavor, the LHA .50% w/ DRN 4 product will require some work to reduce the variation in those flavor scores.  The Multi-Vari Chart is a great choice to demonstrate the results of this study because it shows both the higher average scores for the LHA .50% w/ DRN 4 product and the small amount of variation for the Current product in a clear, concise view.

 

Example 2: Visualizing Data Collected from a Medical Device Manufacturing Process

Now consider that we have collected data from a process where we measure the infusion amount for a medical pump. We have data collected at four different pump speeds across two delivery lines using two different material types. Here is a sample showing how the data are arranged:

Data from a process where we measure the infusion amount for a medical pump

As in the first example, we found the Multi-Vari Chart dialog at Stat > Quality Tools > Multi-Vari Chart… Here we also selected the Standard deviation chart:

The Multi-Vari Chart dialog is found at Stat > Quality Tools > Multi-Vari Chart. Here we also selected the Standard deviation chart.

Visualizing these three factors in a single graph is easy with the Multi-Vari Chart:

Average Infusion Amount with Variation by Pump Speed, Line, Material Code

We can see that the overall average is about 21.5, noted with horizontal line across all levels.  The variability within the pump speed of 1300 shows that the results are below the overall average. We can also see that the infusion measurements were consistently lower for Material Code 9978 across lines One and Two. It is also easy to see that the variability within Pump Speed 1400 is much higher compared to the other pump speeds.

The Multi-Vari Chart also provides an option to create a standard deviation chart of the data – here it is easy to see that the variation when the pump speed is at 1400 is higher across the levels of Line and Material Code.

Standard Deviation of Infusion Amount by Pump Speed, Line, Material Code


Overview and Sample Data Set: See Relationships Between Up to 8 Factors and a Response. Explore Minitab 19 Support


The next steps in this data analysis might be to perform an Analysis of Variance to quantify the observed variation, or to design an experiment to better understand the process. In this example, we had 3 factors. The newly improved Multi-Vari Chart allows you to visualize up to 8 factors at a time.

So, if you have data collected across multiple factors, try the new and improved Multi-Vari Chart in the Quality Tools menu. Visual analytics just got a little easier.