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Statistics in a Nutshell

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

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Statistics in a Nutshell

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  1. Statistics in a Nutshell • Interested in Entire Population • Large Population = Expensive Surveys • Sample a Small Group • Infer Population Characteristics • from Sample Characteristics

  2. 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

  3. 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

  4. Sampling Sampling is faster, cheaper, easier.

  5. 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.

  6. 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 !

  7. Statistics • Descriptive Statistics • Collecting and Analyzing Data • “Tells a story about the numbers” • Inferential Statistics • Drawing conclusions about a population

  8. Descriptive Statistics • Measures of Central tendency • Mean (Arithmetic Average) • Median (Middle Value) • Measures of Variation • Variance • Standard Deviation

  9. 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

  10. Important Statistics • Mean • Tells where the data is centered • Standard Deviation • Tells how far the data is spread out

  11. Family Reunion Babies, youngsters, teenagers young adults, middle-aged parents grandparents, great grandparents Average Age ????? Standard Deviation ?????

  12. 15th High School Reunion Average Age ????? Standard Deviation ?????

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