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Unformatted text preview: Psyc 305 Week 9 Normal Distribution & Probability Goals for Today’s Class At the end of the class you should: • Understand why probability is important in psychology. • Be able to compute probabilities of alternative events. • Be able to compute probabilities of joint/successive events. • Understand how the terms mutually exclusive and independent are relevant. (And see the relationship to correlation.) • See how # of samples and sample size affects distributions. • Know the principles of what makes a normal curve. • Be ready (for next time) to compute percentages of scores falling above, below, or between different values using the normal curve. Statistics 1. Descriptive statistics – simplify, summarize, and organize data 2. Inferential statistics – help us interpret the data and make inferences about the populations represented by the data Why Study Probability in a Course on Research Methods & Statistics? What is a Probability? • A number between 0 and 1 inclusive. 0 p 1 ≤ ≤ • Two ways to think about it: – Expected relative frequency or “longrun relative frequency” – Subjective interpretation (confidence) [apologies to the economists; gambles] What is a Probability? • A number between 0 and 1 inclusive. 0 p 1 ≤ ≤ • Probability vs Proportion vs Percent What is a Probability? • A number between 0 and 1 inclusive. 0 p 1 ≤ ≤ • 0 = impossible • ??? = improbable / unlikely • ??? = possible • ??? = probably / likely • 1 = certain Figuring Probabilities • P (outcome A) = # ways to get outcome A # all possible outcomes • If we flip a fair coin once  what is the p(heads)?...
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This note was uploaded on 09/25/2008 for the course PSYCH 305 taught by Professor Freeman during the Fall '08 term at UVA.
 Fall '08
 FREEMAN
 Psychology

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