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Transparency and consistency
        Jonas Ranstam PhD
Scientific research
A systematic investigation ... designed to develop or contribute to
generalizable knowledge1.

Generalizable: Having predictive and reliable results.

When sampling errors don't exist or are irrelevant, qualitative
research methods (e.g. case reporting) can be used.

If sampling errors do exist, the unavoidable sampling uncertainty
must be quantified (quantitative research) and presented, usually
in terms of p-values and confidence intervals.


1
    The US National Science Foundation
Statistics
Medical researchers rely as never before on statistics for
generating and testing hypotheses and for estimating risks
and benefits of old and new therapies.

Journals can facilitate the writing and reading of research
reports by implementing clear guidelines for manuscript
preparation.
Milestones in scientific publication
1658 – the first scientific journals
1858 – the IMRAD structure
1957 – the abstract
1978 – the Vancouver convention (ICMJE)
1987 – the structured abstract
1997 – the CONSORT guidelines
2007 – the STROBE guidelines
Ten recommendations
 1. Purpose
 2. Data source
 3. Observations
 4. Descriptions
 5. Methods
 6. Assumptions
 7. Significance
 8. Confidence
 9. Multiplicity
10. Claims
1. Purpose
State the research question and the purpose of the study. Is
the ambition to describe an observation, to generate
hypotheses or to test a pre-specified hypothesis?
1. Purpose
State the research question and the purpose of the study. Is
the ambition to describe an observation, to generate
hypotheses or to test a pre-specified hypothesis?

Bad

We have shown that the success rate differs between two
common techniques for autologous chondrocyte implantation.
1. Purpose
State the research question and the purpose of the study. Is
the ambition to describe an observation, to generate
hypotheses or to test a pre-specified hypothesis?

Good

We designed an experiment to test the hypothesis of identical
success rates of two common techniques for autologous
chondrocyte implantation.
2. Data source
Describe the source of subjects, cadavers, animals, tissues,
cell line, etc. and how many of these units have been included
in the study.
2. Data source
Describe the source of subjects, cadavers, animals, tissues,
cell line, etc. and how many of these units have been included
in the study.
Bad

We collected 36 pieces of human cartilage.
2. Data source
Describe the source of subjects, cadavers, animals, tissues,
cell line, etc. and how many of these units have been included
in the study.
Good

Three pieces of cartilage from each of twelve physically active
men between 25 and 75 years of age, previously included as
healthy controls in a clinical trial (ref.), were collected for this
study.
3. Observations
When observations can be presented individually, either
numerically or graphically, this should be preferred. With fewer
than 4 observations it should be the rule.
3. Observations
When observations can be presented individually, either
numerically or graphically, this should be preferred. With fewer
than 4 observations it should be the rule.

Bad
3. Observations
When observations can be presented individually, either
numerically or graphically, this should be preferred. With fewer
than 4 observations it should be the rule.

Good
4. Descriptions
When presenting data in aggregated form, always present the
number of included observations as well as their average and
dispersion. If repeated measurements or replicates are
included, present both the number of independent samples and
the total number of observations.
4. Descriptions
When presenting data in aggregated form, always present the
number of included observations as well as their average and
dispersion. If repeated measurements or replicates are
included, present both the number of independent samples and
the total number of observations.

Bad

The mean change in total knee cartilage volume was 0.62 ml.
4. Descriptions
When presenting data in aggregated form, always present the
number of included observations as well as their average and
dispersion. If repeated measurements or replicates are
included, present both the number of independent samples and
the total number of observations.

Good

The mean change in total knee cartilage volume was 0.62
±1.3 ml (n=24).
5. Methods
Describe all used statistical methods in a statistics section. Use
the original names of the methods. These are not always the
same as the names used in software packages.
5. Methods
Describe all used statistical methods in a statistics section. Use
the original names of the methods. These are not always the
same as the names used in software packages.

Bad

We used the independent groups t-test in the group comparison.
5. Methods
Describe all used statistical methods in a statistics section. Use
the original names of the methods. These are not always the
same as the names used in software packages.

Good

We used Satterthwaite's t-test in the group comparison.
6. Assumptions
The validity of statistical results rely on certain assumptions
being fulfilled. Were they?
6. Assumptions
The validity of statistical results rely on certain assumptions
being fulfilled. Were they?

The man of science has learned to believe in justification, not by
faith, but by verification.

Thomas Huxley, 1866
6. Assumptions
The validity of statistical results rely on certain assumptions
being fulfilled. Were they?

Good

The ANOVA residual was examined using a normal probability
plot, which indicated a Gaussian distribution.

The homogeneity of variance was tested using Levene's test.

The assumption of proportional hazards was investigated using
hypothesis tests of Schoenfeld residuals.
7. Significance
A p-value describes the uncertainty in the generalization (the
outcome of a hypothesis test), and has no relevance for the
observed sample itself.

Distinguish between practical and statistical significance. Clarify
what hypotheses are tested.
7. Significance
A p-value describes the uncertainty in the generalization (the
outcome of a hypothesis test), and has no relevance for the
observed sample itself.

Distinguish between practical and statistical significance. Clarify
what hypotheses are tested.

Bad

There was no difference in mean systolic blood pressure
between treated patients (190 mmHg) and controls (135 mmHg)
(p = 0.06).
7. Significance
A p-value describes the uncertainty in the generalization (the
outcome of a hypothesis test), and has no relevance for the
observed sample itself.

Distinguish between practical and statistical significance. Clarify
what hypotheses are tested.

Good

Treated patients had in this study higher mean systolic blood
pressure than controls, 190 vs. 135 mmHg. The observation,
even if not statistically significant (p = 0.06), raises concern for
future treatment.
8. Confidence
The uncertainty in the generalization of a finding is often better
presented using the two limits of a confidence interval, indicating
plausible values, than one probability of a false positive
conclusion.
8. Confidence
The uncertainty in the generalization of a finding is often better
presented using the two limits of a confidence interval, indicating
plausible values, than one probability of a false positive
conclusion.

Bad

The reproducibility was high (ICC = 0.91; p < 0.0001).
8. Confidence
The uncertainty in the generalization of a finding is often better
presented using the two limits of a confidence interval, indicating
plausible values, than one probability of a false positive
conclusion.

Good

The reproducibility was high (ICC = 0.91; 95%Ci: 0.64 - 0.98).
9. Multiplicity
All departures from the conventional levels of 5% significance
and 95% confidence, like the ones achieved by using one-sided
tests, Bonferroni corrections, and simultaneous confidence
intervals, should be explained and motivated.
9. Multiplicity
All departures from the conventional levels of 5% significance
and 95% confidence, like the ones achieved by using one-sided
tests, Bonferroni corrections, and simultaneous confidence
intervals, should be explained and motivated.
Bad

We have in this randomized trial shown that patients born under
the astrological sign of Gemini benefit aspirin treatment more
than others.
9. Multiplicity
All departures from the conventional levels of 5% significance
and 95% confidence, like the ones achieved by using one-sided
tests, Bonferroni corrections, and simultaneous confidence
intervals, should be explained and motivated.
Good

When multiplicity issues were taken into account, we were
unable to find any interaction between astrological sign and
benefit from aspirin treatment.
10. Claims
The level of statistical rigor (precision and addressed uncertainty
issues) should be consistent with the author's purpose and
conclusions.
What is all this fuss about confidence
intervals and clinical significance?

Questions that can be answered using p-values

- Can I be sure that there is an effect?


Questions that can be answered using confidence intervals

- Can I be sure that there is an effect?

- Can I be sure that there isn't an effect?

- What effect is there?
P-values
Statistical significance
                                    p < 0.05 or n.s.




                           Confidence intervals
                           Statistical and clinical significance




                                                             Effect
                   0
                             Clinically significant effect
Statements that should be avoided
- “Statistical difference”
- “Significant difference”
- “There was no difference”
- “ns” and “p > 0.05”
- “p < 0.03”
Thank you for your attention

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Oac guidelines

  • 1. Transparency and consistency Jonas Ranstam PhD
  • 2. Scientific research A systematic investigation ... designed to develop or contribute to generalizable knowledge1. Generalizable: Having predictive and reliable results. When sampling errors don't exist or are irrelevant, qualitative research methods (e.g. case reporting) can be used. If sampling errors do exist, the unavoidable sampling uncertainty must be quantified (quantitative research) and presented, usually in terms of p-values and confidence intervals. 1 The US National Science Foundation
  • 3. Statistics Medical researchers rely as never before on statistics for generating and testing hypotheses and for estimating risks and benefits of old and new therapies. Journals can facilitate the writing and reading of research reports by implementing clear guidelines for manuscript preparation.
  • 4. Milestones in scientific publication 1658 – the first scientific journals 1858 – the IMRAD structure 1957 – the abstract 1978 – the Vancouver convention (ICMJE) 1987 – the structured abstract 1997 – the CONSORT guidelines 2007 – the STROBE guidelines
  • 5.
  • 6. Ten recommendations 1. Purpose 2. Data source 3. Observations 4. Descriptions 5. Methods 6. Assumptions 7. Significance 8. Confidence 9. Multiplicity 10. Claims
  • 7. 1. Purpose State the research question and the purpose of the study. Is the ambition to describe an observation, to generate hypotheses or to test a pre-specified hypothesis?
  • 8. 1. Purpose State the research question and the purpose of the study. Is the ambition to describe an observation, to generate hypotheses or to test a pre-specified hypothesis? Bad We have shown that the success rate differs between two common techniques for autologous chondrocyte implantation.
  • 9. 1. Purpose State the research question and the purpose of the study. Is the ambition to describe an observation, to generate hypotheses or to test a pre-specified hypothesis? Good We designed an experiment to test the hypothesis of identical success rates of two common techniques for autologous chondrocyte implantation.
  • 10. 2. Data source Describe the source of subjects, cadavers, animals, tissues, cell line, etc. and how many of these units have been included in the study.
  • 11. 2. Data source Describe the source of subjects, cadavers, animals, tissues, cell line, etc. and how many of these units have been included in the study. Bad We collected 36 pieces of human cartilage.
  • 12. 2. Data source Describe the source of subjects, cadavers, animals, tissues, cell line, etc. and how many of these units have been included in the study. Good Three pieces of cartilage from each of twelve physically active men between 25 and 75 years of age, previously included as healthy controls in a clinical trial (ref.), were collected for this study.
  • 13. 3. Observations When observations can be presented individually, either numerically or graphically, this should be preferred. With fewer than 4 observations it should be the rule.
  • 14. 3. Observations When observations can be presented individually, either numerically or graphically, this should be preferred. With fewer than 4 observations it should be the rule. Bad
  • 15. 3. Observations When observations can be presented individually, either numerically or graphically, this should be preferred. With fewer than 4 observations it should be the rule. Good
  • 16. 4. Descriptions When presenting data in aggregated form, always present the number of included observations as well as their average and dispersion. If repeated measurements or replicates are included, present both the number of independent samples and the total number of observations.
  • 17. 4. Descriptions When presenting data in aggregated form, always present the number of included observations as well as their average and dispersion. If repeated measurements or replicates are included, present both the number of independent samples and the total number of observations. Bad The mean change in total knee cartilage volume was 0.62 ml.
  • 18. 4. Descriptions When presenting data in aggregated form, always present the number of included observations as well as their average and dispersion. If repeated measurements or replicates are included, present both the number of independent samples and the total number of observations. Good The mean change in total knee cartilage volume was 0.62 ±1.3 ml (n=24).
  • 19. 5. Methods Describe all used statistical methods in a statistics section. Use the original names of the methods. These are not always the same as the names used in software packages.
  • 20. 5. Methods Describe all used statistical methods in a statistics section. Use the original names of the methods. These are not always the same as the names used in software packages. Bad We used the independent groups t-test in the group comparison.
  • 21. 5. Methods Describe all used statistical methods in a statistics section. Use the original names of the methods. These are not always the same as the names used in software packages. Good We used Satterthwaite's t-test in the group comparison.
  • 22. 6. Assumptions The validity of statistical results rely on certain assumptions being fulfilled. Were they?
  • 23. 6. Assumptions The validity of statistical results rely on certain assumptions being fulfilled. Were they? The man of science has learned to believe in justification, not by faith, but by verification. Thomas Huxley, 1866
  • 24. 6. Assumptions The validity of statistical results rely on certain assumptions being fulfilled. Were they? Good The ANOVA residual was examined using a normal probability plot, which indicated a Gaussian distribution. The homogeneity of variance was tested using Levene's test. The assumption of proportional hazards was investigated using hypothesis tests of Schoenfeld residuals.
  • 25. 7. Significance A p-value describes the uncertainty in the generalization (the outcome of a hypothesis test), and has no relevance for the observed sample itself. Distinguish between practical and statistical significance. Clarify what hypotheses are tested.
  • 26. 7. Significance A p-value describes the uncertainty in the generalization (the outcome of a hypothesis test), and has no relevance for the observed sample itself. Distinguish between practical and statistical significance. Clarify what hypotheses are tested. Bad There was no difference in mean systolic blood pressure between treated patients (190 mmHg) and controls (135 mmHg) (p = 0.06).
  • 27. 7. Significance A p-value describes the uncertainty in the generalization (the outcome of a hypothesis test), and has no relevance for the observed sample itself. Distinguish between practical and statistical significance. Clarify what hypotheses are tested. Good Treated patients had in this study higher mean systolic blood pressure than controls, 190 vs. 135 mmHg. The observation, even if not statistically significant (p = 0.06), raises concern for future treatment.
  • 28. 8. Confidence The uncertainty in the generalization of a finding is often better presented using the two limits of a confidence interval, indicating plausible values, than one probability of a false positive conclusion.
  • 29. 8. Confidence The uncertainty in the generalization of a finding is often better presented using the two limits of a confidence interval, indicating plausible values, than one probability of a false positive conclusion. Bad The reproducibility was high (ICC = 0.91; p < 0.0001).
  • 30. 8. Confidence The uncertainty in the generalization of a finding is often better presented using the two limits of a confidence interval, indicating plausible values, than one probability of a false positive conclusion. Good The reproducibility was high (ICC = 0.91; 95%Ci: 0.64 - 0.98).
  • 31. 9. Multiplicity All departures from the conventional levels of 5% significance and 95% confidence, like the ones achieved by using one-sided tests, Bonferroni corrections, and simultaneous confidence intervals, should be explained and motivated.
  • 32. 9. Multiplicity All departures from the conventional levels of 5% significance and 95% confidence, like the ones achieved by using one-sided tests, Bonferroni corrections, and simultaneous confidence intervals, should be explained and motivated. Bad We have in this randomized trial shown that patients born under the astrological sign of Gemini benefit aspirin treatment more than others.
  • 33. 9. Multiplicity All departures from the conventional levels of 5% significance and 95% confidence, like the ones achieved by using one-sided tests, Bonferroni corrections, and simultaneous confidence intervals, should be explained and motivated. Good When multiplicity issues were taken into account, we were unable to find any interaction between astrological sign and benefit from aspirin treatment.
  • 34. 10. Claims The level of statistical rigor (precision and addressed uncertainty issues) should be consistent with the author's purpose and conclusions.
  • 35. What is all this fuss about confidence intervals and clinical significance? Questions that can be answered using p-values - Can I be sure that there is an effect? Questions that can be answered using confidence intervals - Can I be sure that there is an effect? - Can I be sure that there isn't an effect? - What effect is there?
  • 36. P-values Statistical significance p < 0.05 or n.s. Confidence intervals Statistical and clinical significance Effect 0 Clinically significant effect
  • 37. Statements that should be avoided - “Statistical difference” - “Significant difference” - “There was no difference” - “ns” and “p > 0.05” - “p < 0.03”
  • 38. Thank you for your attention