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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 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, statistics, is represented by counting, measuring, describing, tabulating, ordering, and the taking of censuses-all of which led to modern descriptive statistics. From the influence of the father came modern inferential statistics, which is based squarely on theories of probability.
Describing collections involves tabulating, depicting and describing collections of data. These data may be quantitative such as measures of height, intelligence or grade level------variables that are characterized by an underlying continuum---or the data may represent qualitative variables, such as sex, 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.
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, a school superintendent wishes to determine the proportion of children in a large school system who come to school without breakfast, have been vaccinated for flu, or whatever. Having a little knowledge of statistics, the superintendent would know that it is unnecessary and inefficient to question each child: the proportion for the sample of as few as 100 children. Thus, 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.
美国习惯用语-第790:大摆筵席
美国习惯用语-第17期:To keep one´s shirt&n
美国习惯用语-第783:叫出租车
美国习惯用语-第50讲:to be swept off one&
美国习惯用语-第16期:Right on the beam
美国习惯用语-第41期:to go all out
美国习惯用语-第48讲:to get a foot in&nbs
美国习惯用语-第781:不受欢迎
美国习惯用语-第57讲:lemon and going bananas
美国习惯用语-第37期:to break your neck
美国习惯用语-第789:虚伪
美国习惯用语-第42期:to go for broke
美国习惯用语-第39期:to have a heart
美国习惯用语-第20期:Up in arms
美国习惯用语-第18期:A stuffed shirt
美国习惯用语-第34期:to put all his eggs&
美国习惯用语-第27期:A red letter day
美国习惯用语-第49讲:to stand on one´s&nbs
美国习惯用语-第32期:Singing the blues
美国习惯用语-第23期:To take candy from a
美国习惯用语-第33期:as American as apple 
美国习惯用语-第59讲:a fish out of water
美国习惯用语-第40期:My heart stood still
美国习惯用语-第13期:To keep an ear to&nb
美国习惯用语-第36期:hot seat
美国习惯用语-第26期:A horse laugh
美国习惯用语-第785:新同事
美国习惯用语-第21期:To shake a leg
美国习惯用语-第38期:pain in the neck
美国习惯用语-第786:电影
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