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Unformatted text preview: Psych 100A Week 3 Discussion Notes Dawn Chen October 16, 2009 Probability Terms • Probability : How likely an event is to occur • Outcome : One possible way something could happen; a result of a random experiment • Sample space : The set of all possible outcomes (e.g., the sample space for flipping a coin twice is {HH, HT, TH, TT}) • Event : A subset of the sample space (e.g., the event of getting at least one heads when tossing a coin twice is {HH, HT, TH}) • Probability distribution : Divides the sample space into nonoverlapping portions and assigns a probability to every portion Notation • ( ) P A : Probability of the event A • ( ) P A : Probability of A not occurring • ( ) P A B ∪ : Probability of A or B occurring • ( ) P A B ∩ : Probability of A and B occurring Properties • ( ) 1 P A ≤ ≤ • Every probability distribution sums to 1. Formulas • If every outcome is equally likely, # of outcomes in ( ) total # of outcomes A P A = • If A and B are mutually exclusive, ( ) ( ) ( ) P A B P A P B ∪ = + • If A and B are not mutually exclusive, ( ) ( ) ( ) ( ) P A B P A P B P A B ∪ = + ∩ The Normal Distribution The normal distribution is a theoretical probability distribution that is useful because it approximates many distributions of realworld measures that are determined by a large number of factors, such as IQ. The normal distribution is symmetric , unimodal , and continuous . It extends infinitely to the left and right, always approaching 0 but never quite reaching 0....
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This note was uploaded on 09/24/2010 for the course STATS 13a taught by Professor Chen during the Spring '10 term at UCLA.
 Spring '10
 Chen
 Statistics, Probability

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