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Variables 9/10/2013 Slide 2 Readings Chapter 3 Proposing Explanations, Framing Hypotheses, and Making Comparisons (Pollock) (pp.48-58) Chapter 1 Introduction to SPSS (Pollock Workbook) Slide 3 Homework: Due 9/12 Chapter 1 Question 1 Parts A &B Question 2 Exam 1 9/19.. (study guide for Thursday) Slide 4 About the Homework It must be turned in during class. It cannot be emailed It must appear on the workbook paper (original or a photocopy) You cannot: Slide 5 OPPORTUNITIES TO DISCUSS COURSE CONTENT Slide 6 Office Hours For the Week When Wednesday 10-12:00 Thursday 8-12 And by appointment Slide 7 Course Learning Objectives 1.students will achieve competency in conducting statistical data analysis using the SPSS software program. 2.Students will learn the basics of research design and be able to critically analyze the advantages and disadvantages of different types of design. Slide 8 INDEXES AND SCALES A way of getting content validity Slide 9 Why create a scale/index? To form a composite measure of a complex phenomenon by using two or more items Get at all facets Simplify our data Slide 10 Likert Scale A common way of creating a scale Advantages Disadvantages Slide 11 Guttman Scaling Employs a series of items to produce a score for respondents Ordering questions that become harder to agree with Advantages and disadvantages Slide 12 Guttman Scale Slide 13 SPSS Statistical Package for the Social Sciences Slide 14 What is a statistical package Popular Versions SPSS SAS R Stata Slide 15 Getting SPSS Dont Purchase a student version Limited functions Limited variables Searching the internet for a free version You might get a virus The Russians will steal your identity (exception fallacy). Do Use it on the machines on campus- free! Consider purchasing a 6- month license (52.00 + 4.99 download fee)purchasing Slide 16 How to Open Data files Data Files on the Pollack CD GSS2008.SAV- the 2008 General Social Survey Dataset n=2023 301 variables NES2008.SAV- the National Election Study from 2008. n=2323 302 variables STATES.SAV- aggregate level data for the 50 States. N=50 82 Variables WORLD.SAV- aggregate level data for the nations of the world. n=191 69 Variables Slide 17 SPSS uses 2 windows Data Editor Window is used to define and enter your data and to perform statistical procedures. very spread-sheet like .sav extension The Output Window this is where results of statistical tests appear This opens when you run your first test .spv extension Slide 18 HOW SPSS WORKS Slide 19 It is like a spreadsheet In Variable View You define your parameters Give variables names Operationalize variables We will not do a lot of this Slide 20 Names and Labels Name how the label appears at the top of the column (like the first row in excel) you cant use dashes, special characters or start with numbers These should represent the variable Labels A longer definition of the variable These describe the actual variable Slide 21 Value Labels This shows how variables are operationalized Value= the numeric value given to a category Label= the attribute of the concept Slide 22 In Data View You type in raw data It looks very much like Excel Rows= cases Columns= Variables Slide 23 How Things are Displayed Edit Options Display names Alphabetical Slide 24 Variables I Like Values and Labels Slide 25 Exiting SPSS If you changed the actual dataset you must save it If you ran any statistics, you must save these as well Slide 26 Variables Slide 27 Measured Concepts We need to operationalize concepts to test hypotheses Concept- Conceptual Definition- Operational- Definition- Operationalization- Variable Slide 28 Four Categories of Variables Slide 29 DISCRETE VARIABLES Slide 30 Nominal Variables Identify, label, and operationalize categories Categories are Exhaustive Mutually Exclusive Values are their for quantification only Slide 31 Nominal Examples Slide 32 Ordinal Variables These identify, rank order, label, and operationalize categories The Numbers mean something here Operationalization denotes more or less of an attribute Slide 33 Ordinal Examples Slide 34 Fun While it lasted Slide 35 More Ordinal Fun Slide 36 Health Care Slide 37 Nominal and Ordinal Slide 38 CONTINUOUS VARIABLES Slide 39 What makes them unique The values matter Your variable includes all possible values, not just the ones that you assign. Name, order, and the distances between values matter. Slide 40 Interval Level Variables The values matter at this level The distances matter The zero is arbitrary Slide 41 Examples of Interval Scales Slide 42 Ratio Variables The Full properties of numbers. Its measurement on Steroids Steroids A zero means the absence of a property Classify, order, set units of distance Slide 43 Examples Slide 44 Energy Use Slide 45 Nominal, Ordinal, Ratio Slide 46 DESCRIPTIVE STATISTICS Slide 47 Descriptive Statistics These simply describe the attributes of a single variable. You cannot test here (you need two variables) Why do them? Slide 48 Categories of Descriptive Statistics Measures of Central Tendency The most common, the middle, the average Mean, Median and Mode Measures of Dispersion How wide is our range of data, how close to the middle are the values distributed Range, Variance, Standard Deviation Slide 49 Frequency Distributions This Provides counts and percentages (relative frequencies) of the values for a given variable Computing a relative Frequency The Cumulative Percent is percentage of observations less than or equal to the category Slide 50 Lets Look at this one again Slide 51 Examples St. Edwards Data