Root Cause Analysis

For want of a nail the shoe was lost.          
For want of a shoe the horse was lost.
For want of a horse the rider was lost.
For want of a rider the message was lost
For want of the message the battle was lost.
For want of a battle the kingdom was lost.
And all for the want of a horseshoe

Root Cause Analysis (Wikipedia)              
"General Principle" #3 relaxes an assumption in "How to Analyze"
1    
5 Why (Sixsigma.com)  
5 Whys is a good exdmple of a heuristic: always asking 5 times frees up TAME for other uses that wolld otherwise go for deciding how much information is enough or, worse, getting "all" the information.
Rudyard Kipling's "person small" is an example of the latter
2
Barrier Analysis        (Deaprtment of Energy)The "Barriers" exist to prevent bad things from happening
Joseph Malins
3
Change Analysis       (Deaprtment of Energy) Change analysis is almost the same as Kepner Tregoe. "Is Not" is box 2 on page E-5
4
Causal Factor Tree analysis

5
Failure Mode and Effects Analysis

6
Ishikawa Diagram (Vanderbilt University)

7
Pareto Analysis (Wikipedia)
Pareto Analysis assumes knowledge of how often each of several different potential causes is rpsponsible for a given trouble
8
Fault Tree Analysis