Getting Started with IBM SPSS Stats 20

1. Getting Started with IBM SPSS Stats 20 Presented by: Rosey Zackula Center for Biostatistical Collaboration Office of Research Tuesday, October 23, 2012

2. http://www.rdinfo.org.uk/flowchart/Flowchart.html

3. COURSE OBJECTIVES • Become familiar with the SPSS system • Establish methods for reporting results • Explore steps for analyzing a dataset • Demonstrate the analysis process* • Hands on exercise* * All examples are from Windish and Diener-West, 2005

4. I. WHAT IS IBM SPSS STATS 20? • Comprehensive system for analyzing all types of data • Suite of software tools • Primary purpose • Generate tabulated reports • Produce charts • Plot distributions and trends • Conduct descriptive statistics • Perform complex statistical analyses

5. IBM SPSS System • 16+ Analysis Tools • Statistics Base • Advanced Statistics • Bootstrapping • Categories • Complex Samples • Conjoint • Custom Tables • Data Preparation • Decision Trees • Cont’d • Direct Marketing • Exact Tests • Forecasting • Missing Values • Neural networks • Regression • Amos AND • SamplePower

6. Manuals for SPSS

7. SPSS Help and Support • Help features in SPSS • SPSS Manuals • S:\SPSS Manuals\SPSS 20 • IBM Corp. Web site • http://www.ibm.com/support • USENET discussion group • comp.soft-sys-stat.spss • Center for Biostatistical Collaboration 

8. II. ESTABLISH METHODS FOR REPORTING RESULTS • What style is required? • Check target journal for manuscript • Example JGIM • Modify SPSS output • Edit > Options • Output labeling • Adjust fonts/formats • Table and Charts • Copy special formats (for copying into manuscript: Word, Excel, etc.)

9. III. STEPS TO ANALYZE DATA

10. Step 1: Set up data • Enter manually • Import • Database • Excel, Access, REDCap, Text • Read text • Copy and paste (not advised)

11. Data considerations • SPSS Types • Numeric, comma, dot, scientific notation, date, dollar, custom currency, string, restricted numeric (non-negative integer with leading zeros, i.e. 000001) • Values • Example: categorical variables • 0 = No; 1 = Yes • Measures • Nominal, Ordinal, Scale (data that can be multiplied with meaningful results)

12. Step 2: Inspect data • Role • Input, Target, Both, None, Partition, Split • Defining variable properties • Data attributes • Custom tables • Multiple response: define variable sets (surveys) • Utilities • Variable information • Data file comments • Define/use variables sets

13. Step 3: Clean data • Data preparation • Validation • Identify missing information, unusual cases, etc. • Restructure data • Transform (recoding) • Visual Binning • Create new variables • Compute, recode, replace missing values • Remember to define any new variable properties and attributes

14. Step 4: Describe data Summarizing categorical data • Tables • Dichotomous: proportions • Nominal: relative frequencies (percent of total) • Ordered: median (interquartile range) • Graphs • Bar and pie charts • Percentages vs. Counts

15. Step 4: Describe data (cont’d) Summarizing continuous (scale) data • Tables • Parametric or normal distribution: Mean (standard deviation) • Test of normality • Kolmogorov-Smirnov “vodka test” • Nonparametric test: 1-Sample K-S • K-S Lilliefors (by group) • Explore: Plots • Nonparametric: Median (interquartile range) • Graphs • Histograms, line charts, scatter plots

16. Step 5: Analyze the data • What is the study design? • What is(are) the research question(s)? • Hypothesis to be tested • What is the outcome? • What shape/type of distribution? • Are any groups being compared? • What are the variables of interest? • What shape/type of distribution? • Predictors or confounders?

17. IV. DEMONSTRATION • Study design: randomized clinical trial to evaluate 1-month curriculum • Compare performance of two unpaired groups (intervention and control) • Outcome: composite number of maneuvers performed correctly • Hypothesis 1 • Ho: Participants and controls do not differ in mean number of correct maneuvers

18. V. YOUR TURN • Open SPSS • File > Open Database > New Query… • Database Wizard: Excel Files > Next • Browse… • S:\Everyone\Intro_IBM SPSS_Oct 23 • Intro IBM SPSS_Test data_Windish article.xlsx • Retrieve all Fields > Next > Next • GENDER: Recode to Numeric • Minimize string widths > Finish

19. Your turn (cont’d) • Establish output options per author instructions from target journal • Edit > Options • Define Variables • Data > Define Variable Properties • Variable View • Type, Width, Decimals, Labels, Values, etc. • Choose hypothesis to test • See article Windish and Diener-West, 2005 Hypothesis 2, 3 or 4 (data are not the same; therefore, results may differ)

21. Statistical Results THE GRANDMA CLAUSE You do not really understand something unless you can explain it to your grandmother. Albert Einstein

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23. Reference • A Clinician-Educator’s Roadmap to Choosing and Interpreting Statistical Tests. Windish and Diener-West, 2005 • http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1924630/ • Important downloads from the article: • Table 1: Questions to Consider When Selecting the Appropriate Statistical Test • Appendix A: Diagrammatic Approach to Choosing Summary Measures, Statistical Tests and Methods • Appendix B: Glossary of terms