Gil Harari Statistical considerations in clinical trials

Elephants, Diamonds & Biostatistics ???

Analyses Variables Primary Efficacy Variables Secondary Efficacy Variables Safety Variable Adverse Events. Physical examinations. Laboratory measurements. Reasons for discontinuation.

Statistical considerations in biomedical studies

Is risk factor X associated with disease Y? From the sample, we compute an estimate of the effect of X on Y (e.g., risk ratio if cohort study): - Is the effect real? Did chance play a role?

Why worry about chance? Population Sampling variability… - you only get to pick one sample!

Interpreting the results Population Selection of subjects Inference Make inferences from data collected using laws of probability and statistics - tests of significance (p-value) - confidence intervals

How do we determine if an association is significant? Significance is in context of “Statistical” significance –p-Value –Treatment Effect –Confidence Interval 8

Subjects for Discussion 1.What is a p-Value? 2.Sample Size Calculation 3.Clinical Significance Versus Statistical Significance

Basic Principles of Statistical Analysis Significance Tests Difference Between Treatments Is it by chance? Apply a significance test

Sample Size Calculations

Sample Size Calculation

Based on: 1. Study Design 2. Treatment Effect (Effect Size) (δ) 3. Type I error (α), Type II error (β) 4. Power of the study (1-β)

Clinical significance Versus Statistical Significance CR TA % Improvement 43% 65% Clinical SignificanceStatistical Significance P=0.17 P=0.03 TB CR 52% 41% N = 15N = 60

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