What are Quantitative Assessments?
There is a saying in Lean Six Sigma, “If you can not measure it, you can not improve it”. This means that you cannot be certain whether or not you are successful unless success is defined, measured and tracked. The Quantitative Assessment tools are Lean Six Sigma tools used to quantify and measure a process.
There is a saying in Lean Six Sigma, “If you can not measure it, you can not improve it”. This means that you cannot be certain whether or not you are successful unless success is defined, measured and tracked. The Quantitative Assessment tools are Lean Six Sigma tools used to quantify and measure a process.


Statistical Process Control Demonstration
The example to the right is a randomly generated data from the “piston rings” data set. There are 25 random samplings throughout the day. Each sample group consists of five piston rings randomly selected from the assembly line . The objective is to measure whether or not the diameter of the piston rings are statistically standardized. Questions to Ask:

Graph Interpretations

XBar Chart

Range Chart

Process Capability Plot

QQ Plot
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XBar Chart
An Xbar chart is a statistical tool to measure variation of the sample group means. Control limits help determine the difference between commoncause variation in the mean (natural variation) and specialcause variation in the mean (something changed). If the points pass exceed the control limits (marked in red) or consist of a run violation (marked in yellow), there is a strong chance the process changed and is no longer in statistical control. 
Range Chart
Similar to the xbar chart, the range chart measures the sample group ranges instead of the sample group means. Like the xbar chart, the control limits help determine the difference between commoncause variation in the range (natural variation) and specialcause variation in the range (something changed). If the points pass exceed the control limits (marked in red) or consists of a run violation (marked in yellow), there is a strong chance the process changed and is no longer in statistical control. 
QuantileQuantile Plot
The quantilequantile plot ("QQ plot" for short) helps visual whether or not the distribution of points is normally distributed around the mean. The objective is to have the points line up with the red dashed line. This is important because a large majority of computation for control charts assumes the sampled data points are normally distributed around the mean. 