Setting up and running tests correctly is as much of a science as the statistical analysis. It can go wrong in many ways, which can lead to erroneous and costly decisions. Just taking 3 dimensions - Timing, Selection, Creative - shows 1 way to be right with 6 ways to  be wrong: 

1) Timing correct but Creative Selection missed:
- Timing signals translated correctly but not to the right people the message package was not focused correctly.
+ Focus on better selection and relevancy.
 

2) Creative correct but Timing and Selection missed:
- Marketing has got it right but data has missed the brief.
+ Refine signals (timing) and traits (selection).
 

3) Selection correct but Timing and Creative missed:
- Creative brief not aligned and timing forced.
+ Focus on relevancy.
 

4) Creative missed:
- Data (timing & selection) are correct but creative has missed.
+ Is the appropriate message package available?
 

5) Selection missed:
- Transition from brief to selection to activation has missed.
+ Better test/control loops to remove misses.
 

6) Timing missed:
- Too early or too late by a metre or a mile.
+ Signal (timing) refinement.
 

7) Successful:
+ Excellent! Understand why it worked.