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Everything I wish I had known about research design and data analysis…

Everything I wish I had known about research design and data analysis…. Statlab Workshop Spring 2005 Heather Lord and Melanie Dirks. Outline of a paper. Introduction Theory Data Description Analysis Conclusion. Introduction. Topic Question What is the question you want to answer?

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Everything I wish I had known about research design and data analysis…

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  1. Everything I wish I had known about research design and data analysis… Statlab Workshop Spring 2005 Heather Lord and Melanie Dirks

  2. Outline of a paper Introduction Theory Data Description Analysis Conclusion

  3. Introduction Topic Question What is the question you want to answer? Review the Literature

  4. Theory Categorize your theory • Descriptive or Causal? • Change over time? Write down your theory Identify testable hypotheses from theory Do you need statistics after all? • Quantitative v Qualitative research

  5. Variables Dependent Variable (response, outcome, criterion) Independent Variables (explanatory or predictor variables) Control / Confounding Variables Categorical and Continuous Variables Remember: Types of variables we choose, determine the statistics we use

  6. You need Data Think about analyses early! Collecting your own data • Retrospective, prospective, experimental & observational methods Can find most data you’ll need on-line! Statlab Webpage (http://statlab.stat.yale.edu) • Advisors • Yale StatCat (http://ssrs.yale.edu/statcat/) • ICPSR (http://www.icpsr.umich.edu) • Reference Librarian (Julie Linden)

  7. So, you want to make a survey • Extensive on-line resources and software • Question types determine analyses • Open vs. close ended questions, Likert scales, rank order data • Assumptions of normalcy • Validity • Internal & External validity • Pilot testing • You need variance to analyze! • Sample size • It depends; power, effect size, cost (UCLA power calculator)

  8. Once You’ve Found or Collected your data Download the data and documentation • StatTransfer (Statlab) Determine data file type • Probably a text file (.txt, .dat, .raw) Converting text & delimited files Choose a statistical software program • SPSS

  9. Managing your data Back up all Master Data Files CDR/CDRW, USB Key Codebook • All codes • Adding variables, cases, computing new variables Keep a roadmap • Keep a log of all analyses with what you have done • Save syntax files

  10. Syntax Files What are they? Text-files used to enter commands in bulk Is it worth learning? You will make mistakes, need to make changes SPSS and many other programs let you use pull down menus How do I know what to write? Program’s manual provides the underlying command

  11. So, how do I analyze my data? Correlational design • Correlation allows you to quantify relationships between variables (r, r-squared) • Correlation, partial correlation • Regression allows you predict scores on 1 variable from subjects score on another variable(s) Group differences • t-test & ANOVA • Chi-square for categorical and frequency data Significance v. effect size

  12. Descriptive Statistics Variables Dependent Variable(s) Independent Variable(s) Important Control Variable(s) Graphs Summary Statistics on Key Variables Number, Mean, Minimum, Maximum, Standard Deviation Cross-Tabs

  13. Putting Output into a Paper Cut and Paste Graphs Cut and Paste into Word Processing document Save as .jpeg or .tif file Tables Cut and Paste Format in Word Processing document Import into Excel, format, and then place in Word

  14. More Advanced Analysis Multivariate techniques help to account for confounding factors, allow for testing change over time and more complex hypotheses… (See: Tabachnick & Fidell, Using Multivariate Statistics) • Be honest about your abilities. • Ask for help • Best off including techniques that you fully understand.

  15. Take Away Messages • Determine your question, methods and statistics before you start • Keep a codebook of everything • Back up data • Ask for help • Don’t Get In Over Your Head

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