Basic Statistics(一）[分享]

**Basic Statistics
(Measure Phase)
The Misuse of Statistics
There are three kinds of lies: lies, damned lies, and statistics.
— Benjamin Disraeli —

Figures don’t lie, but liars will figure.
— Charles H Grosvenor —

Statistics are like a bikini. What they reveal is suggestive,
but what they conceal is vital.
— Aaron Levenstein —
The Use of Statistics
The long-range contribution of statistics depends not so much upon getting a lot of highly trained statisticians into industry as it does in creating a statistically minded generation of physicists, chemists, engineers, and others who will in any way have a hand in developing and directing the production processes of tomorrow.
— Walter A Shewhart & Williams E Deming

Statistics is not a substitute for engineering judgement.
— Harold F Dodge
Statistics
Statistics is the branch of science that deals with the collection,
presentation, analysis & interpretation of data for the purpose
of decision-making and problem-solving.

Statistics is a critical skill in quality improvement as statistical
techniques can be used to describe and to understand variability.

Variability
Variability is the result of changes in the conditions under
which observations are made.

Variability can come about due to changes in
material quality
machine settings or conditions
manpower standards
methods of processing
measurement
milieu (environment)
Population vs Sample
Population
the entire set of measurements of interest
Parameters vs Statistics
Parameter Statistic

Mean

Variance

Standard Deviation
Parametric vs Non-Parametric Statistics
Parametric Statistics
- based on the assumption that random samples are selected from populations with a defined (e.g. normal) distribution

Non-Parametric Statistics
- assumes no knowledge whatsoever about the distributions of the underlying populations
- also known as distribution-free statistics
Types of Data — An Overview
Types of Data — Descriptive Orientation
Whether a variable is to be described or be described by other variables.

Response or Dependent Variable
variable under investigation is to be described in terms of other variables

Predictor or Independent Variable
variable is used in conjunction with other variables to describe describe a given response variable**