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Flow charts for correlating research questions to statistical methods

Flow charts for correlating research questions to statistical methods. Is there an association?. Nominal. Relative risk. Scale of measurement of both variables. Ordinal. Spearman’s rho. Yes. T test. Predicting one from another. Numerical. T test. No.

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Flow charts for correlating research questions to statistical methods

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  1. Flow charts for correlating research questions to statistical methods

  2. Is there an association?

  3. Nominal Relative risk Scale of measurement of both variables Ordinal Spearman’s rho Yes T test Predicting one from another Numerical T test No Answers the question: Is there an association?

  4. Is there a difference in measures of association?

  5. Testing r = 0 T test 1 correlation Correlation coefficient Fisher’s z transformation Testing r = value yes Fisher’s z transformation 2 correlations Independent Statistic T test no 1 regression line T test Regression coefficient T test 2 regression lines Answers the question: Is there a difference in measures of association?

  6. Is there a difference in means or medians (ordinal or numerical measures)?

  7. yes T test yes n≥30 T test Normally distributed no 1 group Transform for t or Sign no yes T test yes yes T test yes n≥30 Number of groups Equal variances yes Normally distributed T test no Equal n’s no Transform for t or Wilcoxon rank sum no 2 group no Independent groups Transform for t or Wilcoxon rank sum yes T test (Paired) no yes n≥30 T test (Paired) Normally distributed no Transform for t or Wilcoxon rank sum no Answers the question: Is there a difference in means or medians (ordinal or numeric measurements)?

  8. yes T test yes T test 1 group n≥30 Normally distributed Transform for t or Sign no no yes T test yes Number of groups T test yes Equal variances T test yes n≥30 yes Normally distributed Equal n’s Transform for t or Wilcoxon rank sum no no no Transform for t or Wilcoxon rank sum no Independent groups 2 group yes T test (Paired) yes n≥30 T test (Paired) no Normally distributed no Transform for t or Wilcoxon rank sum no Is there a difference in means or median?

  9. Is there a difference in proportions (nominal measures)?

  10. 1 group np and n(1-p) ≥ 5 Z approximation yes Fisher’s exact test yes Small expected frequencies X2 or z approximation no 2 groups Number of groups Independent groups McNemar or k no yes Collpase categories for X2 yes Small expected frequencies X2 no Independent groups 3 or more groups Cochran’s Q (see book by Sokal and Rohlf no Answers the question: Is there a difference in proportions (nominal measures)?

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