PSC 47410: Data Analysis Workshop What’s the purpose of this exercise? The workshop’s research questions: Who supports war in America? How consistent

PSC 47410: Data Analysis Workshop

What’s the purpose of this exercise? The workshop’s research questions:

Who supports war in America? How consistent is support for conflict across different types of war? Should we be considering other, related questions? If this project were to be

expanded, what could else we look at… how different groups change their support over time, support for other types of conflict, varying patterns in other societies

Will you want to do your research paper on work that builds on this workshop? You research paper assignment will ask you to either do a more complex paper on

public opinion and war or to test the power of various causes of war to explain the outbreak of a conflict not considered in our class readings

How would a research paper using Pew data be different than this assignment with respect to its literature review and what methods you would need to use?

PSC 4000-level Stats Workshop

Where Do You Get Survey Data?

Why are we looking at survey data from the Pew Foundation? How do we download a dataset from Pew?http://people-press.org/category/datasets/?download=20034647

Why do we have to read the methodology sheet first (it’s boring, but critical)? What do we do with the questionnaire?

How does scientific method work?: In theory and in the real world Can we operationalize our dependent variable(s)? Are there some

questions that we can use to identify who supports war? Do we have the independent variable(s) we need? Are there any questions

that identify characteristics (e.g., gender) that we expect to be correlated with whether a person supports war?

What specific hypotheses can we explore with our survey? What specific relationships do we expect to find between our independent and dependent variables?


http://people-press.org/category/datasets/?download=20034647

http://people-press.org/category/datasets/?download=20034647

What Do You Need to Turn In?

Your assignment has two components: The first asks you to complete several data assignments The second is an 1000-word analytical essay

The assignments related to SPSS ask you to: Recode and label both new variables and their response categories You will be asked to create dummy (1-0 value) variables. For example, you can use a

question asking about religion to create a new variable called “Catholic,” where all Catholic respondents are coded 1 and all other respondents are coded zero

Calculate descriptive statistics Mean (the average value of the response categories) Median (the middle value for all of your observations) Mode (the most common response if there’s no natural order to variable’s

response categories) Generate a bar graph Do a little bivariate data analysis using SPSS’s cross-tab routine


Getting Started with SPSS

Open your dataset with SPSS

Open a new syntax file

What are the four SPSS screens you will be working with? Data editor: Data view Data editor: Variable view The syntax file (Why is it WAY better than just pointing and

clicking all of the time? Why is this the ONLY file that you will want to save in most cases? )

The output file


Recoding Data in SPSS

Why do we need to recode? Need to drop refusals (but we want to be careful to think about what “don’t know

means… e.g. if someone doesn’t know that she’s a born-again Christian, she’s not one) Variables may not measure constructs correctly, so we need to create different

categories that make sense We’ll want to create dummy (0-1) variables

How do we recode? Use the point and click menus at the top of the data editor Use the “Recode Into Different Variable” option Select variable you want to recode Tell SPSS how you want to recode the variable

Name and label the new variable Define values

Do not hit OK; instead, you want to paste command into syntax Highlight the appropriate syntax and click the run (arrow) button


Recoding Data: Step by Step Illustration












Labeling Values in SPSS

Why do we need to label the values used for different response categories (e.g., 1=male, 0=woman)? You may not remember how you recoded values Labels will transfer into tables and graphs

How do we label values for our variable categories? Use “Define Variable Properties” option Select variable(s) with values you want to label Tell SPSS how you want to label the values Paste command into syntax Highlight syntax and click run Once you’ve got the syntax down, you may want to work much more quickly

with other variables by copying and pasting that syntax and making appropriate substitutions


Creating Value Labels for Response Categories:

Step by Step Illustration














Descriptive Statistics in SPSS

What descriptive statistics may interest us? Frequencies Mean (the average), Medians (the middle observation), and Mode (rarely

used)

How do we compute descriptive statistics? Use “Descriptive Statistics” option Select “Frequencies” Select variable(s) that you want to analyze Select “Statistics” Select the statistics you want to view Option 1 (if you will need the results later): click the paste command to create

syntax; highlight the syntax and click run Option 2 (if you are using the results right now): click OK and the syntax won’t

be pasted into your syntax file, but the output will be created


Descriptive Statistics: Step by Step Illustration


Descriptive Statistics












Graphing in SPSS

What kinds of graphs might we create? Bar Line Histogram

How do we compute descriptive statistics? Use “Descriptive Statistics” option Select “Frequencies” Select variable(s) that you want to analyze Select “Charts” Select the charts you want to view; check the “percentage” option in most

cases so that your charts will be more readable Paste command into syntax Highlight syntax and click run


Creating Graphs


Creating Graphs


Creating Graphs


Creating Graphs


Creating Graphs


Creating Graphs


Creating Graphs


Bivariate Analysis in SPSS

What types of bivariate analysis might we conduct? Correlation Crosstabs (this is your best option for tables that will make

sense to a general audience) Significance tests

How do we conduct bivariate analysis? Use options in the “Analyze” menu Select variable(s) that you want analyze Tell SPSS how you want to analyze the values Paste command into syntax Highlight syntax and click run


Calculating Correlation










Guidelines for Correlation

Less than .1: Very weak relationship

.1 to .2: Weak relationship

.2 to .3: Moderate relationship

Above .4: Strong relationship


Review: Variable Types

Categorical Represent categories or names (e.g. gender, religion)

Ordinal Rank ordered indicators (e.g. agree, strongly agree)

Interval Ordered values where all unit increases are roughly

equivalent (e.g. age)


Calculating Significance

Crosstabs will allow you to see relationships between two variables in more detail Put dependent variable in the rows Put independent variable in the columns

Can also test association: Categorical/categorical: Lambda, Cramer’s V Categorical/ordinal: Cramer’s V Ordinal/ordinal: Gamma, Tau-B (same number of categories) Categorical/Interval: Eta Ordinal/Interval: Spearman’s Rho Interval/Interval: Pearson’s R


Crosstabs and Tests of Significance
















Documents

PSC 47410: Data Analysis Workshop What’s the purpose of this exercise? The workshop’s research questions: Who supports war in America? How consistent