PSY201 9.11.13 To Post

Stascal terminology varies for sample stascs versus

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Unformatted text preview: to make inferences about… on the basis of a par@cular sample   Sample: a part of the popula@on for which a researcher collects data and knows a set of scores 10 9/10/13   Why do we study samples, rather than a popula@on?   Prac@cality   Goal is to make generaliza@ons or predic@ons about events beyond our reach   Try to study a sample of people who are representa@ve of the popula@on of interest   Random selec@on is ideal   From the full popula@on of interest, randomly select individuals to be included in sample   OCen is imprac@cal or impossible to obtain a truly random sample ▪  Instead, try to get a sample that is not systema@cally unrepresenta@ve of popula@on in any known way ▪  Avoid haphazard selec@on   Sta@s@cal terminology varies for sample sta@s@cs versus popula@on parameters Population Parameter Sample Statistics Scores from entire population Scores of sample only (Usually unknown) (Calculated from known data) µ (mu) M σ (sigma) SD (sigma squared) SD 2 Mean Standard Deviation Variance σ2 11 9/10/13   Probability defini@on: Expected rela@ve frequency of an outcome   Outcome: result of experiment/situa@on   Frequency: how many @mes something happens   Rela@ve frequency: number of @mes something happens rela@ve to the number of @mes it could have happened   Expected rela@ve frequency: what you expect to get in the long run if you repeat the experiment/situa@on many @mes   Long ­run rela@ve frequency interpreta@on of probability vs. subjec@ve interpreta@on of probability   Probability = Possible successful outcomes All possible outcomes What is the probability of genng a 4 when you roll a die? 1/7 = 0.14 What is the probability of choosing a heart from a deck of cards? 13/52 = 1/4 = 0.25   Range: 0 to 1, also represented 0 ­100%   Probability as the likelihood of occurrence   Impossible to Certain 12 9/10/13   Probability is symbolized as the le]er p, and usually represented as a decimal (0 to 1) rather than a percent   p = .5 represents a 50/50 chance   p < .05 represents “the probability is less than .05”   The normal distribu@on can be thought of as a probability distribu@on 15 70 85 100 115 130   You apply to 20 graduate programs, 10 of which are in clinical psychology, 5 of which are in counseling psychology, and 5 of which are in social work. You get a message from home that you received a le]er from one of the programs. Give the probabili@es that it is from   A clinical psychology program.   A counseling psychology program.   From any other program besides social work. 13 9/10/13   A student wants to study the effect of stress on memory. He posts a sign ­up sheet for anyone willing to par@cipate. The student is conduc@ng: a.  Random selec@on b.  Haphazard selec@on c.  Specified selec@on d.  Quota selec@on   In sta@s@cal language, a scoop of water drawn from a fish tank full of tropical saltwater fish to determine the exact salt content of the water is: a.  Popula@on b.  Parameter c.  Sample d.  Popula@on distribu@on   In a normal curve, approximately __?__ percentage of scores are lower than 2 standard devia@ons below the mean.   In a normal curve, approximately 68% of the scores are between a z ­score of __?__ and a z ­score of __?__.   In a normal curve, what percentage of scores fall within 2 standard devia@ons of the mean? 14...
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This note was uploaded on 03/24/2014 for the course PSY 21201 taught by Professor Bernard during the Winter '13 term at SUNY Stony Brook.

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