**The analysis phase is purely mathematical. It is during this phase that we set up a set of tools to identify the real cause of the problem.**

## Introduction

The analysis phase is purely mathematical. It is during this phase that we set up a set of tools to identify the real cause of the problem.

For this, the mathematical tools at our disposal are numerous. It is a question of choosing them wisely according to the problem encountered, the possible measures, the means, the context … these tools, go simple tools of the problem solving: diagram of correlation, diagram **Ishikawa**… to the more complex tools below.

**Do you know what a statistician says with feet in the embers and head in a bucket of cold water ?**

**” On average I am well “**

## 1. Descriptive statistics

The methods of **descriptive statistics** allow studies to be carried out on the basis of exhaustive data, ie concerning all individuals in the study population^{1}. Simpler than **inferential statistics**, we find notions of Mean, standard deviation or Variance.

## 2. Inference statistics

Les **inferential statistics** refer to the procedures by which we generalize the information of a sample to the population from which it was drawn. It is in this type of statistics that we find tools such as :

## 3. Validate the cause

Set up the case verification plan by testing. The important thing is to be able to reproduce the problem wisely.

## Good questions to ask at the end of this phase

- Do we have the root cause of the problem ?
- Is it root causes or only symptoms ?
- Do we know how to reproduce the defect ?
- Are we in tune with the expectations of the project ?

## Source

1 – E. Bressoud, J. C. Kahane (2010) – Statistique descriptive

J.N. Gillot (2012) – La gestion des processus métier

C. Frechet (2011) – Mettre en œuvre le Six Sigma

W. Fox (1999) – Statistiques sociales

N. Volck (2011) – Déployer et exploiter Lean Six Sigma

R. Basu (2011) – Fit Six Sigma : A Lean approach to building sustainable quality beyond Six Sigma

T. Burton, J. L. Sams (2005) – Six Sigma for small and midsized organizations

M. Pillet (2013) – Six Sigma : comment l’appliquer