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幽幽草 发表于 2007-4-18 17:18

Statistics

[size=3][color=#29384e][font=Times New Roman]There were two widely divergent influences on the early development of statistical methods. Statistics had a mother who was dedicated to keeping orderly records of government units [/font][font=宋体]([/font][font=Times New Roman]states and statistics come from the same Latin root status[/font][font=宋体])[/font][font=Times New Roman] and a gentlemanly gambling father who relied on mathematics to increase his skill at playing the odds in games of chance. The influence of the mother on the offspring[/font][font=宋体],[/font][font=Times New Roman] statistics[/font][font=宋体],[/font][font=Times New Roman] is represented by counting[/font][font=宋体],[/font][font=Times New Roman] measuring[/font][font=宋体],[/font][font=Times New Roman] describing[/font][font=宋体],[/font][font=Times New Roman] tabulating[/font][font=宋体],[/font][font=Times New Roman] ordering[/font][font=宋体],[/font][font=Times New Roman] and the taking of censuses[/font][font=宋体]—[/font][font=Times New Roman]all of which led to modern descriptive statistics. From the influence of the father came modern inferential statistics[/font][font=宋体],[/font][font=Times New Roman] which is based squarely on theories of probability.[/font][/color][/size]
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[size=3][color=#29384e][font=宋体]  [/font][font=Times New Roman]Describing collections involves tabulating[/font][font=宋体],[/font][font=Times New Roman] depicting and describing collections of data. These data may be quantitative such as measures of height[/font][font=宋体],[/font][font=Times New Roman] intelligence or grade level[/font][font=宋体]——[/font][font=Times New Roman]variables that are characterized by an underlying continuum[/font][font=宋体]——[/font][font=Times New Roman]or the data may represent qualitative variables[/font][font=宋体],[/font][font=Times New Roman] such as sex[/font][font=宋体],[/font][font=Times New Roman] college major or personality type. Large masses of data must generally undergo a process of summarization or reduction before they are comprehensible. Descriptive statistics is a tool for describing or summarizing or reducing to comprehensible form the properties of an otherwise unwieldy mass of data.[/font][/color][/size]
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[color=#29384e][font=宋体][size=10.5pt]  [/size][/font][size=10.5pt]Inferential statistics is a formalized body of methods for solving another class of problems that present great of problems characteristically involves attempts to make predictions using a sample of observations. For example[/size][font=宋体][size=10.5pt],[/size][/font][size=10.5pt] a school superintendent wishes to determine the proportion of children in a large school system who come to school without breakfast[/size][font=宋体][size=10.5pt],[/size][/font][size=10.5pt] have been vaccinated for flu[/size][font=宋体][size=10.5pt],[/size][/font][size=10.5pt] or whatever. Having a little knowledge of statistics[/size][font=宋体][size=10.5pt],[/size][/font][size=10.5pt] the superintendent would know that it is unnecessary and inefficient to question each child[/size][font=宋体][size=10.5pt]:[/size][/font][size=10.5pt] the proportion for the sample of as few as 100 children. Thus [/size][font=宋体][size=10.5pt],[/size][/font][size=10.5pt] the purpose of inferential statistics is to predict or estimate characteristics of a population from a knowledge of the characteristics of only a sample of the population[/size][/color]

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