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David Normando A PowerPoint®-based guide to assist in choosing the suitable statistical test. NOTE: This presentation has the main purpose to assist researchers.

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Presentation on theme: "David Normando A PowerPoint®-based guide to assist in choosing the suitable statistical test. NOTE: This presentation has the main purpose to assist researchers."— Presentation transcript:

1 David Normando A PowerPoint®-based guide to assist in choosing the suitable statistical test. NOTE: This presentation has the main purpose to assist researchers and students in choosing the appropriate statistical test for studies that examine one variable (Univariate). Some multivariates analyses are also included. Please proceed to the next page... If you have any suggestion, criticism, please contact the author by

2 David Normando What do you want to do? For an answer, click on the button 1)I want to assess whether my data have a Normal distribution 2)I want to compare groups (Looking for differences between samples) 3)I want to make correlation or regression analysis between variables. 4)I want to check the replicability of data (analysis of random and systematic error) 5)I would choose the appropriate graph to my data.

3 David Normando Normal distribution is requested when using continuos data and n<30 Tests for Data Analysis Distribution- Normality Normal distribution is requested when using continuos data and n<30 You may choose the test according to sample size. Use DAgostino, if n10 Use DAgostino, if n10 Use DAgostino-Pearson, if n20 Use DAgostino-Pearson, if n20 Use Lilliefors or Shapiro-Wilk, Use Lilliefors or Shapiro-Wilk, for any n value for any n value Back to beginning Back to beginning

4 David Normando What kind of data you have? (Click on the button). Nominal Ordinal NUMERICAL Continuous Nonparametric Categorical data Parametric (mean) Ex: height / length / weight (Assuming a normal distribution on n>30) Ex: Frequency: Yes / No Race Gender Ex: Middle (1) / Moderate(2) Severe (3) Comparing groups (samples) Back to beginning Back to beginning How to check Normality ? How to check Normality ?

5 David Normando Numerical Data (parametric) If the distribution is not Normal, skip to "Abnormal" ABNORMAL How many groups (samples) do you have? 1 2 >2

6 David Normando Are your samples paired or dependent? No Yes Not sure? Dependent Samples mean: Before X After Left Side X Right Side T1 x T 2 x T3 Numerical Data (parametric) If the distribution is not Normal, skip to "Abnormal" ABNORMAL

7 David Normando Answer: one sample t test Back to beginning Back to beginning Numerical Data (parametric) If the distribution is not Normal, skip to "Abnormal" ABNORMAL

8 David Normando Answer: Independent t test or ANOVA. Back to beginning Back to beginning Numerical Data (parametric) If the distribution is not Normal, skip to "Abnormal" ABNORMAL

9 David Normando Answer: Paired t test or ANOVA for repeated measurements.. Back to beginning Back to beginning Numerical Data (parametric) If the distribution is not Normal, skip to "Abnormal" ABNORMAL

10 David Normando Answer: Analysis of Variance (ANOVA) or MANOVA (Multiple Analysis of Variance), if you have >1 variable. Numerical Data (parametric) If the distribution is not Normal, skip to "Abnormal" ABNORMAL Back to beginning Back to beginning

11 David Normando Ordinal Categorical Data (Nonparametric) 2 >2 How many groups (samples) do you have ?

12 David Normando No Yes Ordinal Categorical Data (Nonparametric) Not sure? Dependent Samples mean: Before X After Left Side X Right Side T1 x T 2 x T3 Are your samples paired or dependent?

13 David Normando No Yes Ordinal Categorical Data (Nonparametric) Not sure? Dependent Samples mean: Before X After Left Side X Right Side T1 x T 2 x T3 Are your samples paired or dependent?

14 David Normando Answer: Mann-Whitney test Back to beginning Back to beginning Ordinal Categorical Data (Nonparametric)

15 David Normando Answer: Wilcoxon (signed rank test) or Signal test. Back to beginning Back to beginning Ordinal Categorical Data (Nonparametric)

16 David Normando Answer: Kruskal-Wallis Test Back to beginning Back to beginning Ordinal Categorical Data (Nonparametric)

17 David Normando Answer: Friedmans Test Back to beginning Back to beginning Ordinal Categorical Data (Nonparametric)

18 David Normando Nominal Categorical Data (Nonparametric) 2 >2 How many groups (samples) do you have ?

19 David Normando No Yes Nominal Categorical Data (Nonparametric) Not sure? Dependent Samples mean: Before X After Left Side X Right Side T1 x T 2 x T3 Are your samples paired or dependent?

20 David Normando No Yes Nominal Categorical Data (Nonparametric) Not sure? If some of the cells in the contingency table give values (expected) lower than 5. Is there any expected value <5 ?

21 David Normando No Yes Nominal Categorical Data (Nonparametric) Not sure? Dependent Samples mean: Before X After Left Side X Right Side T1 x T 2 x T3 Are your samples paired or dependent?

22 David Normando Answer: Chi-square (x²) test or Binomial Test, if using 2 samples and proportion (%) Back to beginning Back to beginning Nominal Categorical Data (Nonparametric)

23 David Normando Answer: Cochrans test (absolute or relative frequence: %) Nominal Categorical Data (Nonparametric) Back to beginning Back to beginning

24 David Normando Answer: McNemars test Back to beginning Back to beginning Nominal Categorical Data (Nonparametric)

25 David Normando Answer: Exact Fishers test Nominal Categorical Data (Nonparametric) Back to beginning Back to beginning

26 David Normando Correlation or Regression Analysis Ordinals Numerical Nominal What kind of data you have? (Click on the button). Ex: height / length / weight (Assuming a normal distribution) Ex: Frequency: Yes / No Race Gender Ex: Middle (1) / Moderate(2) Severe (3) How to check Normality ? How to check Normality ? Nonparametric Categorical data Parametric (mean)

27 David Normando Numerical Data (parametric) If the distribution is not Normal, skip to "Abnormal" ABNORMAL How many variables do you have? 2 >2

28 David Normando Answer: Pearsons Correlation Simple Linear Regression Back to beginning Back to beginning ABNORMAL Correlation tests or regression analysis to Continuos data If the distribution is not Normal, skip to "Abnormal"

29 David Normando Answer: Pearsons Correlation (parcial) or Canonical Correlation Multiple Linear Regression Back to beginning Back to beginning ABNORMAL NOTE: For Correlation all variables examined must have a Normal Distribution. For Linear Regression dependent variable must have a Normal Distribution How to check Normality ? How to check Normality ? Correlation tests or regression analysis to Continuos data If the distribution is not Normal, skip to "Abnormal"

30 David Normando Answer : Spearman or Kendal Correlation Back to beginning Back to beginning Correlation test to Ordinal data (nonparametric)

31 David Normando How many variables do you have? 2 >2 Correlation and Regression Analysis to Nominal data (nonparametric)

32 David Normando Answer: Contingency coefficient C Simple Logistic Regression Correlation test to Nominal data (nonparametric) Back to beginning Back to beginning

33 David Normando Answer: Contingency coefficient C Multiple Logistic Regression Correlation test to Nominal data (nonparametric) Back to beginning Back to beginning

34 David Normando Replicability or Reproducibility (Systematic error) Ordinal Numerical Nominal What kind of data you have? (Click on the button). Ex: height / length / weight (Assuming a normal distribution) Ex: Frequency: Yes / No Race Gender Ex: Middle (1) / Moderate(2) Severe (3) Nonparametric Categorical data Parametric (mean) How to check Normality ? How to check Normality ?

35 David Normando Answer: Parametric test for dependent data Note: Intraclass correlation can be used, if you would like to check the association between 2 or more measurements. Replicability or Reproducibility (Systematic error for numerical data) 2 samples 2 samples >2 samples >2 samples ABNORMAL Back to beginning Back to beginning For random or casual error, you may use TEM (technical error measurement): D= difference between repeated measures n=number of individuals

36 David Normando Answer: Weighted Kappa Replicability or Reproducibility (Systematic error for ordinal data) 2 sample> 2 samples NOTE: in case of an ordinal variable, nonparametric tests for paired or dependent data can also be used Back to beginning Back to beginning

37 David Normando Answer: Kappa Back to beginning Back to beginning Replicability or Reproducibility (Systematic error for Nominal data)

38 David Normando Nominal Ordinal Numerical Parametric (mean) Graph Selection What kind of data you have? (Click on the button). Ex: height / length / weight (Assuming a normal distribution) Ex: Frequency: Yes / No Race Gender Ex: Middle (1) / Moderate(2) Severe (3) Back to beginning Back to beginning Nonparametric Categorical data

39 David Normando Comparing Independent Samples Making Data Correlation or regression Comparing Dependent Samples (paired) Graph Selection Not sure? Dependent Samples mean: Before X After Left Side X Right Side T1 x T 2 x T3

40 David Normando BOX-PLOT - Comparing Groups. Continuous or Ordinal Data (Score) This chart describes the measure of central tendency (MEAN for continuos data or MEDIAN for Ordinal data), measures of dispersion (Standard deviation for parametric data or interquartiles deviation for Ordinal data) and the whiskers (maximum and minimum values ) Back Outlier: an observation that is numerically distant from the rest of the data.

41 David Normando Line graph for longitudinal data This chart describes the measure of central tendency (mean for Continuos data or median for Ordinal data) longitudinally Back

42 David Normando Graphic for Correlation Tests or Regression Analysis Back

43 David Normando Bar/Column Graphic Nominal data (frequency) Back


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