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PS 225 Lecture 17

PS 225 Lecture 17. Comparing Two Variables. In-Class Analysis. Independence vs. Dependence. Independence: Variables are not related Dependence: Variables demonstrate correlation Independent Variable Dependent Variable. Chi-Squared Statistic. Hypothesis Test for Independence.

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PS 225 Lecture 17

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  1. PS 225Lecture 17 Comparing Two Variables

  2. In-Class Analysis

  3. Independence vs. Dependence • Independence: Variables are not related • Dependence: Variables demonstrate correlation • Independent Variable • Dependent Variable

  4. Chi-Squared Statistic

  5. Hypothesis Test for Independence • Ho: Variables are Independent • H1: Variables are Dependent

  6. SPSS Chi-Square Test

  7. Hypothesis Test for Independence Result • Reject Ho and conclude H1 : Variables are dependent • Don’t Reject Ho : Not enough information to conclude variables are dependent

  8. Chi-Squared Test • Test for independence • Can be used for nominal and ordinal data • Nonparametric test

  9. Conditional Distribution

  10. Extreme Conditional Distributions • No Association • Perfect Association

  11. Measures for Nominal Variables • Phi (Φ) for 2x2 tables • Cramer’s V for larger tables

  12. Phi (Φ)

  13. Phi (Φ) • Between 0 and 1 • 0 No Correlation • 1 Perfect Correlation

  14. Guidelines for Interpreting Phi • Less than 0.10 : Weak • Between 0.10 to 0.30 : Moderate • Greater than 0.30 : Strong

  15. Cramer’s V

  16. Cramer’s V • Between 0 and 1 • 0 No Correlation • 1 Perfect Correlation

  17. Guidelines for Cramer’s V • Less than 0.10 : Weak • Between 0.10 to 0.30 : Moderate • Greater than 0.30 : Strong

  18. Measures for Nominal Variables • Phi (Φ) for 2x2 tables • Cramer’s V for larger tables

  19. Measures for Ordinal Variables • Gamma- for collapsed ordinal variables • Spearman’s Rho – for continuous ordinal variables

  20. Gamma • Increase in accuracy of prediction • 0-0.3 weak • 0.31 to 0.6 moderate • Greater than 0.61 strong • Sign indicates strength

  21. Spearman’s Rho • Proportionate Reduction in Error (PRE)

  22. Robert Putnam • Political Scientist at Harvard University • Studies Social Capital, “features of social life- networks, norms and trust- that enable participants to act together effectively to pursue shared objectives”

  23. Reading for Next Class • Get Article from JSTOR • Tuning In, Tuning Out: The Strange Disappearance of Social Capital in America • Robert D. Putnam • PS: Political Science and Politics, Vol. 28, No. 4. (Dec., 1995), pp. 664-683.

  24. SPSS Assignment • What characteristics of individuals might increase or decrease the likelihood they will engage in activities that build social capital like visiting neighbors (socommun2) or friends (socfrend2)? • Choose three survey responses to study • Conduct a Chi-Squared hypothesis test for independence • Give your hypotheses, test results and interpretation • Characterize the relationship using a measure of association • Clearly indicate which measure you use and give the relative size of the impact of the independent variable.

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