1. Statistical analysis Christian Gratzke LMU Munich
Outline for Cathy
Hier Foto Ausgabe EU Focus
Christian Gratzke
LMU Munich
Department of Urology
London, March 2017

2. Urologists usually have a limited training in biostatistics
Statistical Analysis
Urologists usually have a limited training in biostatistics
Statistics departments offer introductory courses to the world of biostatistics
These courses are recommended before / when starting to conduct research

3. I usually do my statistics myself
Statistical Analysis
I usually do my statistics myself
However, I always contact my biostatistician to double-check the results

4. Very complex statistical tests are seldom useful
Statistical Analysis
Very complex statistical tests are seldom useful
Whenever used, they should be explained and referenced
Fancy statistics are meaningless if not strictly related with the clinical problem
What might be hard for an experienced reviewer will be impossible to understand for most of the readers

5. Statistical Analysis

6. Statistical Analysis

7. Slip Ups – and how to avoid them
Dr. Andrew Vickers, Ph.D.
Attending Research Methodologist
MSKCC

8. Slip Up 1
It is not only about producing p values

9. Statistical Methods Inference Is something there?
Hypothesis testing: p values
Estimation
How big is it?
E.g. means, correlations, proportions, differences between groups

10. Statisticians can also help with…
Thinking through the scientific question
Experimental design
Data collection
Data quality assurance

11. Inference
State a null hypothesis

12. Inference
State a null hypothesis
Get your data, calculate p value

13. Inference State a null hypothesis Get your data, calculate p value
If p<5%, reject null hypothesis
If p ≥5%, don’t reject null hypothesis

14. Slip Up 2 Don’t accept the null hypothesis
In a court case: guilty or not guilty
In a statistical test: reject or don’t reject

15. Slip up 3
RESULTS: Compared with a BMI of 18.5 to 21.9 kg/m2 at age 18 years, the hazard ratio for premature death was 2.79 (CI, to 3.81) for a BMI of 30 kg/m2 or greater.
CONCLUSION: Moderately higher adiposity at age 18 years is associated with increased premature death in younger and middle-aged U.S. women

16. Slip up 3
A result isn’t a conclusion

17. Slip up 4
Mean gestational time was weeks in the experimental group compared to weeks in controls (p=0.6945).

18. Slip up 4
Every number you write down means something

19. Slip up 5
Whereas Erk3, ECAD, P21, P53, Cadherin, il 6, il12 and Jak had no association with outcome (p>0.2 for all), Ki67 was a predictor of recurrence (p=0.03). We recommend that Ki67 be measured to determined eligibility for adjuvant chemotherapy.

20. Slip up 5
Multiple testing. Looked at 9 different biomarkers. 35% chance of at least one marker with p<0.05.
A statistical association isn’t grounds for a change in practice.

22. Thank you