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Chapter 1

Chapter 1 - Chapter 1 Overview and Descriptive Statistics...

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Chapter 1. Overview and Descriptive Statistics Statistical concepts and methods - useful - indispensable in understanding the world. Discipline of Statistics - how to make intelligent judgments and informed decisions in the presence of Uncertainty and Variation - statistical methods are needed Without uncertainty or variation, no need for statistical methods - every component has the same lifetime, all resistors have the same resistance value - a single observation reveal all desired information 1

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Variation example – emission test on motor vehicle Results for one vehicle HC(gm/mile) 13.8 18.3 32.2 32.5 CO(gm/mile) 118 149 323 236 - substantial variation on HC and CO Statistics offers - methods for analyzing the results of experiments - suggestions for how the experiments can be performed in an efficient manner to mitigate the effects of variation & have a better chance of producing correct conclusions 2
1.1 Populations, Samples, and Processes Data – collection of facts produced in experiments Population – a collection of objects which the experiment is interested in All gelatin capsules of a particular type produced in a specified period. All individuals who received a B.S. in engineering during 2005. Census – desired information is available for all objects in the Population - practically impossible or infeasible Sample – a subset of population 3

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- selected in some prescribed manner - to obtain the desired information of certain characteristics of the objects in a population Variable – any characteristic whose value may change from one object to another - denote by a lower case letter, x,y,z Data – observed value on a variable Univariate data – observations on a single variable Univariate categorical(attribute, qualitative) data Type of transmission: M A A A M A A M A A Univariate numerical(variable, quantitative) data Lifetime of batteries(hr.s): 5.6 5.1 6.2 6.0 … Bivariate data – observations on two variables (height, weight): (72, 168) (75,212) … 4
Multivariate data – observations on more than two variables Descriptive statistics – method to summarize and describe important features of data - graphics (histogram, boxplot) - calculation of numerical measures (mean, standard deviation, correlation coefficient) statistical software packages ( MINITAB , SAS, SPSS) Ex 1.1) tragedy of space shuttle Challenger X=O-ring temperature - How the temperatures are distributed?

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Chapter 1 - Chapter 1 Overview and Descriptive Statistics...

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