Not all statistics are the same. It’s useful to discern between the various types of statistics when doing analysis. Remember;

- a statistic is a value obtained from the sample or a calculation.
- a parameter is a value found or estimated from the population.

## Analytical statistics aka Inferential Statistics

- Sometimes it is unrealistic to get an exhaustive population study – ex. all of America so we use a sample to infer something about the whole.
- Most of the time we infer something about the whole population.
- Developing a confidence interval is an example of using Analytical statistics.
- Also known as inferential statistics.
- http://www.sixsigmadaily.com/terms/inferential-statistics

### What are Inferential Statistics?

### When do you use Inferential Statistics??

### Examples of Inferential Statistics in a DMAIC Project

## Descriptive statistics (aka Enumerative statistics)

## What are Descriptive Statistics?

- Typically used for the whole entire population, not just a sample.
- Using a graph or population parameter
- Organize or summarize information
- Mean, median, mode
- Graphs, charts & plots

### When do you use Descriptive Statistics??

### Examples of Descriptive Statistics in a DMAIC Project

(Walkthrough each one listed with an example)

## Assumptive statistics

- No such thing.

## Helpful Articles

http://www.micquality.com/six_sigma_glossary/analytical_descriptive_statistics.htm (Descriptive vs. inferential statistics)

## ASQ Six Sigma Green Belt Kinds of Statistics Questions

**Question:** The statistics that summarize a population are referred to as

(A) categorical statistics

(B) descriptive statistics

(C) probabilistic statistics

(D) control statistics

**Answer:** (B) Descriptive statistics summarize a population. The other options are nonsensical.

## Comments (2)

3. The percentages of total quality cost are distributed as follows: prevention 12%, appraisal 28%, internal failure 40%, and external failure 20%. One would conclude:

a. More money should be invested in prevention

b. Expenditures for failures are excessive

c. The amount spent for appraisal seems about right

d. Nothing

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