Central tendency is the idea that when using normal data, all three of the main measures (mean, mode, median) tend to be roughly the same.
Standard deviation is the measure of variation in a process. Describing variation by standard deviations lets us easily compare processes.
A stem and leaf plot is a technique to categorize either continuous or discrete values. It is used to organize data as they are collected.
In the Analyze phase of DMAIC, we want to use the 6M’s in Six Sigma (Six Ms or 5Ms and one P or 5M1P). This helps root out defects.