Six Sigma documentation refers to documents that contain details about the project. It is a tool to gather facts & thoughts in a formal way.
A Scatter Analysis is used when you need to compare two data sets against each other to see if there is a relationship.
Linear regression is a statistical technique to estimate the relationship between a dependent variable and an independent variable.
The T distribution and T tests are used to determine the likelihood of various conditions occurring for small sample sizes (<=30).
Analysis of Variance (ANOVA) is a parametric statistical technique that compares data sets. They evaluate the means of three or more factors.