Statistical Analysis Tools in Six Sigma - Scatter Plot

What is a Scatter Plot?

A scatter plot is a graphical representation that displays the relationship between two numerical variables. It uses a Cartesian coordinate system, with one variable plotted on the x-axis and the other on the y-axis. The data points are represented by individual dots, and their positions on the plot reveal the values of both variables for each data point.

When to use a Scatter Plot?

Scatter plots are especially useful when you want to explore and understand the relationship between two continuous variables. They help answer questions such as:

  • Is there a correlation between the two variables?
  • Are there any patterns or trends in the data?
  • Do outliers exist within the data set?
  • Are there any clusters or groups of data points?

Leveraging Scatter Plots for Quality Improvement

1. Visualizing Relationships:

Scatter plots provide a clear visual representation of how two variables interact. In addition, they enable you to quickly identify trends, patterns, or any unusual data points, giving you a deeper understanding of the data at hand.

2. Correlation Analysis:

Scatter plots help determine the strength and direction of the relationship between variables. By observing the general trend of the plotted points, you can identify whether the variables are positively, negatively, or not correlated at all.

3. Outlier Detection:

Outliers are data points that deviate significantly from the general pattern. Scatter plots allow you to easily spot outliers. Generally, this may indicate errors in data collection or highlight unique instances that require further investigation.

4. Data Clustering:

Scatter plots can reveal clusters or groups of data points that share similar characteristics. As a result, this insight can be valuable for identifying subgroups within the data or detecting patterns that are not immediately apparent.

Example of a Scatter Plot

Sales Performance: In the business world, scatter plots can help explore the connection between advertising expenses and product sales. By plotting advertising spending on the x-axis and sales figures on the y-axis, you can determine whether increased advertising investment leads to higher sales volumes.

scatter plot

How to interpret a Scatter Plot?

By plotting the given data points on a scatter plot with advertising expenses on the x-axis and product sales on the y-axis, we can interpret the relationship between these variables.

1. Positive Relationship:

Overall, there appears to be a positive relationship between advertising expenses and product sales. As advertising expenses increase, there is a tendency for product sales to also increase. This can be seen by the general upward trend of the data points on the scatter plot.

2. Outliers:

There are a few outliers in the data set. Specifically, these outliers represent instances where the relationship between advertising expenses and product sales deviates from the general trend. In addition, they may indicate unique circumstances or other influential factors affecting sales independent of advertising expenses.

3. Clustering:

The data points seem to cluster around certain regions of the scatter plot. Further, this clustering suggests that certain ranges of advertising expenses correspond to specific ranges of product sales. In addition, it may imply that there are optimal advertising spending levels that yield the best sales results.

4. Variation:

While there is a positive trend, it’s important to note that there is some variation in the data. In fact, even at similar advertising expense levels, product sales can vary. Also, this variation may be due to other factors such as market conditions, product quality, or competition.

Overall, based on the scatter plot, we can conclude that increasing advertising expenses tend to have a positive impact on product sales. However, it’s crucial to consider other factors and outliers that may influence sales performance. Further analysis and exploration of the data would provide a more comprehensive understanding of the relationship between advertising expenses and product sales.


In summary, scatter plots are an invaluable tool for visualizing relationships between numerical variables. With their ability to simplify complex data sets and reveal hidden patterns, scatter plots empower both experts and beginners to gain insights quickly. By utilizing scatter plots, you can uncover connections, identify outliers, and extract meaningful information from your data, ultimately enhancing decision-making and driving progress in diverse fields.

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