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Statistics in a Nutshell Interested in Entire Population Large Population = Expensive Surveys Sample a Small Group – Infer Population Characteristics – from Sample Characteristics Examples Exit polls on election day Marketing surveys for new products Medical trials for new vaccines Neilson ratings of television shows Air measurements for pollutants Definitions Population --- Universe (Entire Group) Parameter Numeric Characteristic of a Population Average, Variance, Standard Deviation, etc Sample --- Subgroup of the Population Statistic Numeric Characteristic of a Sample Average, Variance, Standard Deviation, etc Sampling Sampling is faster, cheaper, easier. Sampling Sampling is faster, cheaper, easier. Hope, that the sample is representative of the population; and therefore, the sample statistic is an accurate estimate of the population parameter. Sampling Sampling is faster, cheaper, easier. Hope, that the sample is representative of the population; and therefore, the sample statistic is an accurate estimate of the population parameter. If the sample is not representative of the population, then all bets are off ! Statistics Descriptive Statistics – Collecting and Analyzing Data – “Tells a story about the numbers” Inferential Statistics – Drawing conclusions about a population Descriptive Statistics Measures of Central tendency – Mean (Arithmetic Average) – Median (Middle Value) Measures of Variation – Variance – Standard Deviation Measures of Central Tendency Mean – – – – Arithmetic Average Balance Point Basis for other statistics Influenced by extremes Median – Middle Value – Different Balance Point – Not influenced by extremes Important Statistics Mean – Tells where the data is centered Standard Deviation – Tells how far the data is spread out Family Reunion Babies, youngsters, teenagers young adults, middle-aged parents grandparents, great grandparents Average Age ????? Standard Deviation ????? 15th High School Reunion Average Age ????? Standard Deviation ?????
