PSYC301-01Sept15Lecture(ForPosting)

# PSYC301-01Sept15Lecture(ForPosting) - PUREMEM 1 2 3 4 If...

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PUREMEM 1. If psychologists want to give the representative value of a variable based on the scores in a sample, they usually give the mean . 2. If you are given the variance for a sample, you can calculate the SD simply by doing what? Taking the square root of the variance 3. If you measure the exact same behavior in two different samples and you find that scores are more variable in Sample B than in Sample A, then it must be that both the variance and the standard deviation are larger in Sample B than in Sample A. 4. The SD is the number that gives the average amount by which scores in a sample differ from the mean .

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Calculating standard deviation using Excel If you want to quickly determine the standard deviation of a group of scores, do the following: 1) Enter the scores in Microsoft Excel, one number per cell 2) In any empty cell, type this: =stdev( 3) Using the mouse, select all the cells containing the group of scores 4) In the cell where you previously typed =stdev, now add this: ) 5) Press Enter and a number will appear in the cell That number is the standard deviation
Z scores

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Describing samples After collecting data about numeric variables from a random sample of people, you can now do 4 things: 1. Show how scores are distributed over all the possible values of the variable By making a histogram 2. Describe the shape of the distribution Unimodal, multimodal, symmetrical, skewed 3. Give the representative value of the variable Mean or mode (but usually the mean) 4. Describe amount of variability among scores Variance or SD All 4 are ways of describing the whole sample
Describing individual scores within a sample Next you will learn a descriptive statistic that allows you to say something interesting about individual scores

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## This note was uploaded on 10/04/2011 for the course PSYC 301 taught by Professor Keithlyle during the Spring '11 term at University of Louisville.

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PSYC301-01Sept15Lecture(ForPosting) - PUREMEM 1 2 3 4 If...

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