540201Statistics for Engineer

Statistics Deals with

Collection Presentation Analysis and use of data to make decision Solve problems and design products and

processes Can be powerful tool for

Designing new products and systems Improving existing design Designing, developing and improving

production processes

Variability

Collecting Engineering Data Retrospective Study

Would be either all or a sample of the historical process data.

Observational Study Would be either observations of process or

population. Are usually conducted for short time

period. Designed Experiments

Collect the observations of the resulting system output data.

Random Samples Statistical methods work correctly and

produce valid results. Random samples must be used.

Each possible sample of size n has an equally likely chance of being selected.

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Population and Sample Population

◦ An entire group of objects that have been made or will be made, described by a characteristic of interest

◦ Population parameters are unknown and usually unknowable Sample

◦ The group of objects actually measured in a statistical study◦ A sample is usually a subset of the population of interest◦ Sample statistics estimate population parameters

“Population Parameters” “Sample Statistics”m = Population mean

s = Sample standard deviation

Sample

Population

s = Population standard deviation

X = Sample mean

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Population and Sample

Probability(sampling)

Inference(predict)

Population

Parameters:, , r, etc.

Sample

Statistics:x, s, p, r, etc.

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Data type Attribute data

–Discrete, proportion and count of defects are the most common

–We can count Variable data

–Continuous data–We can measure variablesVariable data ให้�ข้�อมู�ลที่�

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ParametersPopulation Sample

Mean µ

Variance S2 or SD2

Standard Deviation S or SD

Standard score Z