What is a scatter plot, and how is it used in Six Sigma?
Lets get into this with a little more detail. The scatter plot is also known in the world of manufacturing as the scattergram or scatter diagram. This is a basic graphic tool. The tool is used to illustrate a specific relationship between two variables.
Ok, lots of fancy words. Here it is. These dots show where something was, as far as numbers of the function, and where something went to in that same function, and the relationship of those changes.
For example: If the overall production team was able to produce 500 cars before stating the Six Sigma plan. Then with the changes in waste reduction created a change of an additional 200 cars in the same amount of time. Then the numbers would show that there was a 200-point increase. This increase could have been due to the relationship of changes that occurred with the implementation of Six Sigma.
There are a few parts that are included in the scatter plot that make it very nice for working the data. First of all there is not a need for the plot to have specified dependent and independent variables. This means that either of the variable types that are being used can be placed on either axis.
The scatter plot can be used to show that there is a relationship involved with the variables. However it cannot necessarily prove that one relationship is the cause of the other.
This is mainly because the relationship can be there. However, there are also other determining factors that can occur in the situation that may have more affect then simply one change or another.
With the same example above you can see that if there was a promotion of one kind or another. Therefore increasing the motivation of the employees. With the result of the increase of overall productivity, well at least on some level. Therefore you could see how the numbers could be affected in the overall scatter plot.
There are several ways that the measurements of numbers can show changes. There are several factors that come in to play that make it difficult to say that one specific thing would change data. Here is some things that they plotting allows for.
1. Whether there is a relationship or not
When the information is compiled, there will be places that may cluster; join etc, then those numbers can show relative information that is needed for those statistics. Thus showing positive or negative movements that are being taken.
In Six Sigma, you will find that a scatter plot, among other tools is used to identify and correct problems that occur. Also, to track the changes when the problems are worked with. Thus offering evidence to change and productivity.