Lecture6 Normal Distribution & Z-Scores

Lecture6 Normal Distribution & Z-Scores - Normal...

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Normal Distributions & Z-Scores (introduction to inferential statistics) Lecture 6
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Today Descriptive vs. inferential statistics Empirical vs. theoretical distributions Probability The normal distribution Proportionality
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Descriptive vs. Inferential statistics Descriptive statistics: Describe the data with graphs, words, and numbers that indicate the middle and spread of the data Inferential statistics: Uses what we know about a sample to infer about the larger population, using the concept of probability
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Distributions Empirical distributions Scores that come from observations (real data). Theoretical distributions Hypothetical scores that come from math formulas and logic.
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Probability Basic question: what are the odds? Varies from 0 (impossible) to 1 (certain) THE PROBABILITY SCALE +-----------------------------------+---------------------------------+ 0 .5 1 Event will not occur Just as likely for event to occur or not occur Event always will occur
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Probability A ratio of success or failure to total number of events: Example: If I role a die, there is 1/6 chance that I will role a 3. success Total events p =
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Odds Probability is often expressed as odds Example from the upcoming Masters There’s 9-2 odds that Tiger will win. Odds = Probability of event will not occur Probability event will occur Or, Probability Tiger will not win Probability Tiger will win
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Linking probability and distributions Empirical approach to probability: observe events; look at ratio of success Theoretical approach to probability: find the area under a theoretical curve
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theoretical distributions As the number of observations increase, the empirical distribution comes closer and
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Lecture6 Normal Distribution & Z-Scores - Normal...

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