Biostatistics
Quantitative Qualitative
Observational Studies Descriptive
Case Study/Report Case-Series
Analytical Ecological Study Cross-sectional Study Longitudinal Study
Case Control (Retrospective) Nested Case Control Cohort (Prospective) Historical Cohort
Descriptive Qualitative Case Study Case Report/Series
Traditional Qualitative
Historical research Phenomenological research Grounded theory research Ethnographical research
Meta-synthesis
Experimental Studies Pre-Experimental Quasi-experimental True Experimental
Meta-analysis
Correlational Studies
Multi-Method /Mixed Method
Component Design Integrated Design
QUANTITATIVE Pre-experimental
Uncontrolled Experimental Study
(Single Group Post Test Only)
Self Controlled Experimental Study
(Within Group Pre-Post Test)
Quasi-experimental
Controlled Study
• Between Groups Non-equivalent Post Test Only
• Between Groups Non-equivalent Pre-Post Test
Trials with External Controls
Factorial Design
True experimental Randomized Controlled Trial (RCT)
Completely Randomized Design (CRD)
Randomized Complete Block Design (RCBD)
Onset of Study
Time
Sequential Control (Crossover Design)
X X X X
Intervention
X X X X Washout
period
Experimental subjects
Controls
Phases of a Full Clinical Trial
• Phase I: finalizes the treatment (e.g., to determine things like drug dose and safety)
• Phase II: seeks preliminary evidence of effectiveness
• Phase III: fully tests the treatment (randomized clinical trial or RCT)
• Phase IV: focuses on long-term consequences of the treatment
DESCRIPTIVE STATISTICS
• Descriptive Measures
• Tabular Presentation
• Graphical Presentation
• Textual Presentation
Descriptive Measures
• Measures of the Middle (Central Tendency)
• Measures of Variability (Dispersion)
• Measures of Position
• Measures of Association
• Measures of Ratios and Proportions
• Measures of Disease Frequency and Association
Variability • Range = (Highest – Lowest)
• Variance = Mean of Squared Deviations
• Standard Deviation = Square Root of Variance
• Coefficient of Variation = standard deviation divided by mean times 100
• Kurtosis
• Skewness
Association Numerical & Numerical Pearson’s Product Moment Correlation Coefficient
Numerical & Binary Point-Biserial Correlation Coefficient
Ordinal and Ordinal Spearman’s Rank Correlation Coefficient
Kendall’s Tau Rank Correlation
Ordinal and binary Rank Biserial Correlation
Binary and Binary Phi Coefficient
Strength of Linear Association
0
1
0.5
0.4
0.8
weak relationship (0.01 – 0.39)
strong relationship (0.80 – 0.99)
moderate relationship (0.40 – 0.79)
perfect linear relationship
no linear relationship
Descriptive Measures
• Central Tendency: Mean, Median, Mode
• Dispersion: Variance, Standard Deviation, Coefficient of Variation, Kurtosis, Skewness
• Position: Percentiles, Deciles, Quartiles, Z Score
• Association: Correlation Coefficients
• Ratios and Proportions
• Disease Frequency: Incidence and Prevalence
tables
• Simple Frequency Tables • Contingency Table / Cross-Tabulation • Dummy Tables • Master Tables • Summary Tables
Graphical Presentation
• Bar Graphs
• Line Graphs
• Scatter/Dot Plots
• Pie/Circle Graphs
• Pictogram / Cartogram
• Cluster Diagram
Radar Chart, Web chart, Spider chart, Star chart, Cobweb chart, Star plot, Irregular polygon, Polar chart,
or Kiviat diagram
T Tests
• Small sample test
• With sample size <30
• For large samples use Z Test
• Assumptions include
– Random sampling
– Sufficient sample size (do sample size estimation)
– Normal distribution of data
T Tests and Alternatives
One sample T Test Sign Test
Paired (Dependent) sample T Test
Wilcoxon Signed Rank Test or Mann-Whitney U Test
Two (Independent) samples T Test
Wilcoxon Rank Sum Test
Parametric Tests Non Parametric Tests
Chi Square Test
Types - • One Random Sample: Test of Goodness of Fit • One Random Sample, Two Group Comparison: Test of independence • Two Random Samples: Test of Homogeneity
Alternatives to Chi square Test
• Merge Columns or Rows
• Fisher’s Exact Test (applicable only to 2X2 table, more than 20%
less than 5 and with zero)
• McNemar’s Test (Dependent samples)
One way ANOVA Compare two or more groups
Example: Compare the waist-hip ratio among sedentary, semi-active and active people
Require Post Hoc Tests when significant
• Example: Tukey’s HSD
Correlational Statistics
• Correlation Coefficients
• Regression Analysis
– Correlation Coefficients + Prediction
• Note: only establishes associations (functional relationships)
• Limited by data of sample
Multivariate Statistics * Many Groups of Data * Many Variables
1. Inferential Methods: ANOVA & ANCOVA
2. Regression Methods
3. Classification Methods
4. True Multivariate Methods:
MANOVA & Canonical Correlation
5. Meta-analysis
ANOVA Multiple Independent Single Dependent
ANCOVA Single or Multiple Independent Single Dependent Co-variables (Confounders)
Linear Regression
Independent Dependent
Many
Numerical or
Categorical
One
Numerical
Multiple Regression
One or Many
Numerical or
Categorical
One
Binary
Binary Logistic/Logit Regression
One or Many
Numerical or
Categorical
One
Categorical
Multinomial Logistic Regression
One or Many
Categorical
One
Categorical
Log Linear Analysis
Multivariate Statistics
Classification Methods
• DISCRIMINANT FUNCTION ANALYSIS
• Factor Analysis (example: Principal Component Analysis)
• Cluster Analysis
• CLASSIFICATION AND REGRESSION TREE ANALYSIS (CART)
MULTIVARIATE ANALYSIS OF VARIANCE
• Simply called as “ANOVA with many dependent variables”
CANONICAL CORRELATION ANALYSIS
• the correlation of two canonical (latent) variables, one representing a set of independent variables, the other a set of dependent variables