I learned statistics back in the university then never applied concepts  and after some 10 years I was challenged to undertake basic statistics  matters in the way of learning Six Sigma. This book is very focused on  the variation and the graphical interpretation of data. Yuo may read  this book over a weekend then attack Six Sima stats without pain. 
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Understanding Variation: The Key to Managing Chaos (2nd Edition)
Labels: Six Sigma