# How efficient is an estimator?

**Sommaire de notre article**

### How efficient is an estimator?

One **efficient estimator is** characterized by a small variance or root mean square error, indicating a small deviation between the estimated value and the “true” value.

### How to demonstrate that an estimator is unbiased?

Definition: A **estimator** ˆθ of θ **is** said **without bias** if: E(ˆθ) = θ, ∀θ ∈ Θ. Thus, this condition of absence of **bias** ensures **that**over time, situations where the**estimator** overestimates and underestimates θ will balance each other out, so **that** the estimated value will be correct on average.

### What is Sigma’s level of bottle production?

The “sigma level” of our bottle production (assuming all controls give more or less the same results) would be around 5.72 here. The implementation of a 6-sigma approach in a company corresponds to an extremely strong signal of management’s desire to improve quality.

### What is the sigma method?

It is a statistical concept. 1 Sigma is the standard deviation (the area around the mean). The goal is that the quality process is almost absolute reliability, therefore ensuring reliability up to 6 times the standard deviation. The Six Sigma method was created for Motorola.

### What is Six Sigma?

What does the term Six Sigma mean? Before the term six sigma became the name of the famous method, it was a simple statistical reference to the Gaussian curve (or normal law) which specifies the dispersion of a data series around the mean.

### What is the purpose of the Six Sigma method?

The goal is that the quality process is almost absolute reliability, therefore ensuring reliability up to 6 times the standard deviation. The Six Sigma method was created for Motorola.