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Primer on statistical reporting and analyses for continuous variables

Primer on statistical reporting and analyses for continuous variables. Giuseppe Biondi Zoccai University of Turin, Turin , Italy gbiondizoccai@gmail.com. SCOPE OF THE PROBLEM.

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Primer on statistical reporting and analyses for continuous variables

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  1. Primer on statistical reporting and analyses for continuous variables Giuseppe Biondi Zoccai University of Turin, Turin, Italy gbiondizoccai@gmail.com

  2. SCOPE OF THE PROBLEM • Continuous variables are very common (e.g. age, left ventricular ejection fraction, hemoglobin concentration, hematocrit, late loss at angiographic analyses) • Their reporting and analysis strongly depends on the underlying distribution (Gaussian [i.e. normal] versus non-Gaussian)

  3. ALGORITHM • Check if variable is well known for having Gaussian distribution • If yes and sample size > 30 then proceed to point 2. • If no or sample size < 30 then proceed to point 3. • Report variable as mean±standard deviation and compare it with Gossett-Student t test

  4. ALGORITHM • Compare variable distribution with Gaussian distribution using one-sample Kolmogodorov-Smirnov test • If p>0.05 then go back to point 2. • If p<0.05 then go back to point If no or sample size < 30 then proceed to point 4. • Report variable as median (1°-3° quartile) and compare it with Mann-Whitney U test (for indepent samples) or Wilcoxon rank-sum test (for related samples)

  5. ALGORITHM • If instead than 2 groups, several groups are being compared, other tests should be employed, including ANOVA, MANOVA, or ANCOVA (after transformation) versus Kruskal-Wallis or Friedman non-parametric tests

  6. KOLMOGODOROV-SMIRNOV TEST

  7. KOLMOGODOROV-SMIRNOV TEST

  8. KOLMOGODOROV-SMIRNOV TEST

  9. GOSSETT-STUDENT T TEST

  10. GOSSETT-STUDENT T TEST

  11. GOSSETT-STUDENT T TEST

  12. MANN-WHITNEY U TEST

  13. MANN-WHITNEY U TEST

  14. MANN-WHITNEY U TEST

  15. Thank you for your attentionFor any correspondence: gbiondizoccai@gmail.comFor these and further slides on these topics feel free to visit the metcardio.org website:http://www.metcardio.org/slides.html

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