Psychological Statistics PSY 3204
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This 17 page Class Notes was uploaded by Ms. Beverly Doyle on Wednesday September 23, 2015. The Class Notes belongs to PSY 3204 at University of South Florida taught by Staff in Fall. Since its upload, it has received 14 views. For similar materials see /class/212678/psy-3204-university-of-south-florida in Psychlogy at University of South Florida.
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Date Created: 09/23/15
Today s Agenda El Frequency distribution tables El Creating graphs of distributions for different types of variables continuous vs discrete D Size and shape of distributions II Stem amp leafBox plot 1132011 Frequency Distribution Ta ble The number of participants who Age of the participants reported the given age The percentage of your Th t f sample that reported a e percen age 0 your sam e that re orteol a Iven a e g 9 given age and ages below a t 39 l IEQUEHE PEVEEM Percent Vaild 1E 49 34 5 B 25 19 7 20 21 15 i gt 21 1D 7 2 22 1 7 9 33 4 1 9 24 4 2 G 15 I i 4 IE 4 7 5 17 1 7 18 1 7 29 1 7 30 1 7 3i 3 2 Z 32 7 33 1 7 Total 139 1EU U Frlquoncy Vaim Missing Tuiai temate mate Tuiai Svstem undlr 1132011 1132011 Histogram Continuous Variables I X g A J 39JOJgtOT v IIJgtOOI Frequency i 2 3 4 5 Quiz scores number correct Histogram Continuous Variables Histogram MeanZU4 381 33M D With continuous data we usually draw a smooth curve instead of the iagged shapes produced by we histograms Frequency 1 Normal Distribution n El Ideally our data will be normally distributed El A perfectly normal distribution is less common than a blizzard in Key Largo Central Tendency Mode 8 most Mod bequem number quot Matte Madlan Mean Mean l5 average or Median rs middle numbey in its 5 numbers symmetrical dislnbuliun asymmetrical dislnbullun El Where is the center of the distribution El Different definitions of center will result in different values more on that next week 1132011 Variability The Nnrmal Bell Curve Frequency x Data iI Both curves have the same center and the same number of cases El But scores unoler the reel curve are more spread out from the center than scores unoler the blue curve Skew Skewed distributions Positive skew Negative skew C Your data are usually at least somewhat skewed ii Especially common for items with floors age of college students income or ceilings test scores 1132011 1132011 Kurtosis I What is the shape of your distribution I Is it too flat Or too skinny Other Figures Stem amp Leaf 1quot 2393 Data Stern and Leaf Display A sel of N 1 24 SL UI39ES presented as raw data and 83 82 63 3 23 organized in a stem and leaf 62 93 78 4 26 display 7 68 33 5 6279 76 52 97 6 283 85 42 46 7 1643846 32 57 59 8 352 56 73 74 9 37 74 81 76 Other Figures Stem amp Leaf ege Stem andLeaf Plot Frequency Stem 5 Leaf 4a DU 18 UUUDUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU 2 6 00 19 DDDDODDDUOUDOUUUDDODDUDOUU 21nn 2n anunnunnnnnnnnnnnnnun 1D DEI 2 1 anuanuuuu 11 DD 22 uuunnuununu UEI 23 4 DU 24 0000 Z 230 5 DU 131w Extremes gtzs Stem width E5 1 ch leaf 1 case is I Stem width tells you that the stem is the number in the is place of the value of the variable 50 18 is 18 Other Figures Stem amp Leaf AGE or RESPONDENT seemeenaeneet Plat Frequency Stem 5 Leaf aaaaaggggggggggggg uuuuuuuuuuuuuuuu111111111112zzzzzzzzzz223333333333344444444444 555555556666666666667777777777788888888889999999999 55555778800000 5 casElS El Stem width tells you that the stem is the number in the 105 place of the value of the variable 50 l is 10 2 is 20 etc I Each leaf represents five cases 1132011 1132011 Other Figures Box Plot El Box shows the middle 50 of the data D The line in the middle is the median midpoint more on that next week El Whiskers denote the location of the minimum Total Metric Score and maximum values CI Sometimes displayed horizontally Other Figures Box Plot Hulaium A An u l 39lt 1 Circles and stars denote possible outliers extreme scores that can cause problems D Numbers identify person in the data set with the extreme score Other Figures Box Plo r 1132011 Introduction to Statistics T Andrew Caswell Week 1 January 18 2011 Today s Agenda What is Statistics I Who do psychologists study I What information do we collect How 00 we conecr me information 1132011 What is Statistics What are the four goals of Psychology Describe behavior 2 Explain behavior 3 Predict behavior 4 Controlchange behavior I What is Statistics Statistics is a tool of research I A set of mathematical procedures for organizing summarizing and interpreting information I What is happening Why is it happening I What will happen in the future I How can we change what is happening 1132011 Who do psychologists study Population vs Sample A population is the set ofall the individuals in a particular study I A sample is a set of individuals selected from a population usually Intended to represent the population in a research study THE POPULATION All of the individuals of interest The results The sample from the sample is selected from are generalized The populo rion to the population THE SAMPLE The individuals selected to participate in the research study 1132011 I What information do psychologists collect When we study samples we measure variables I A variable is a characteristic or condition that changes or has different values for different individuals I Types of Variables Variables can be classi ed as discrete or continuous Discrete Variables consist of indivisible categories such as ethnicity Continuous Variables are in nitely divisible into whatever units a researcher may choose For example time can be measured to the nearest minute second halfsecond etc 1132011 1132011 I Variables in Populations amp Samples Sample Population 100 USF College Students American College Students Statistic Parameter Mean Mean M or X mu We calculate statistics because we don t know the parameters I HOW do psychologists collect information I Look at relationships between variables The independent variables IV causes or explains the dependent variable DV The value ofthe DV is dependent on the value of the IV l Alcohol Consumption amp GPA I IV Alcohol Consumption I DV GPA I Your alcohol consumption has a negative effect on your GPA I How do psychologists collect information I Usually employ one of two study designs I Correlational Study I Experiment 1132011 l Correlational Studies A correlational study simply observes the two variables as they exist naturally I The relationship between alcohol consumption and GPA I Alcohol Consumption amp GPA IV Alcohol Consumption DV GPA Your alcohol consumption has a negative effect on your GPA 1132011 I Experiments The goal of an experiment is to demonstrate a causeandeffect relationship between two variables that is to show that changing the value of one variable causes changes to occur in a second variable The effects of alcohol consumption on memory I Alcohol Consumption amp Test Performance IV Number of margaritas consumed 0 2V 4 DV Performance on a memory Test Did one group 0 2 4 out perform others 1132011
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