Final Presentation starts TODAY!

1. Final Presentation starts TODAY!

2. Designing a New Study: IV. Experiments

3. Chapter 11 (p110 -127) • The randomized blinded trial (RBT) • Special types of randomized blinded design • Other experimental designs • Deciding to do an experiment

4. THE RANDOMIZED BLINDED TRIAL (RBT) THE FUTURE THE PRESENT No Disease Disease Treatment Randomize Population No Disease Control (Placebo) Disease Sample Steps: 1. Select a sample from the population 2. Measure baseline variables 3. Randomize 4. Apply intervention (one should be a blinded placebo, if possible. 5. Follow up the cohorts 6. Measure outcome variables (blindly, if possible)

5. Assembling the study cohort • Define inclusion criteria that are appropriate to the research question. • Define exclusion criteria that will help control errors. • Design an adequate sample size and plan the recruitment accordingly. Sample

6. Measuring baseline variable • Characterize the study cohort • Consider measuring the outcome variable • Measuring various predictors of outcome Sample

7. Randomizing the study subjects • a true random allocation • tamperproof • example • Using the last digit of each number in a column of random number • Representing the three study groups with 0, 1, & 2, • Reading down each column in sequence, • Skipping over the numbers 3-9 until the first 0,1, or 2 is reached, and • Assigning the participant to that group. Randomize

8. Applying the intervention • Importance of blinding • Choice of a comparison group • Assuring compliance Treatment Control (Placebo)

9. Measuring the outcome • Appropriateness to the research question • Statistical characteristics • Number of outcome variables • Importance of blinding No Disease Disease No Disease Disease

10. Analyzing the results • Testing the hypothesis • X2 • t-test • or whatever • intention-to-treat • subgroup analyses • early stopping rules No Disease Disease No Disease Disease

11. Special types of randomized blinded designs • Run-in design • Factorial design • Randomization of matched pairs • Pre-randomization • Group randomization

12. Run-in design No Disease Disease Treatment Randomize Placebo No Disease Control (Placebo) Disease Sample Population Non compliance

13. Factorial design Population Drug A & Drug B Disease No Disease Drug A & Plac.B Disease No Disease Plac.A & Drug B Disease No Disease Plac. A & B Disease No Disease Sample A factorial design RBT, providing two studies for the price for one

14. And others • Randomization of matched pairs • Pre-randomization • Group randomization • Nonrandomized between-group designs • Unmeasured confounding variables (e.g., life-style) cannot be fully removed by statistical adjustment • pseudo random mechanism • Nonblinded between-group designs • Time series designs • Natural experiments

15. Deciding to do an experiment • Strategies for answering the research question with observational studies have been exhausted. • The existing knowledge is not sufficient to determine clinical or public health policy. • An experiment is likely to provide an important extension of this knowledge.