Statistics in Brief: The Importance of Sample Size in the Planning and Interpretation of Medical Research

Biau, David; Kernéis, Solen; Porcher, Raphaël

doi:10.1007/s11999-008-0346-9

Cited by 292 publications

(217 citation statements)

References 27 publications

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“…3, Point D). Sample size can be used as a lever to control for Types I and II error levels [2]. However, a strong statistical association, p values, or test statistics never imply any causal effect.…”

Section: Implications For Researchmentioning

confidence: 99%

P Value and the Theory of Hypothesis Testing: An Explanation for New Researchers

Biau

Jolles

Porcher

2010

Clinical Orthopaedics &Amp; Related Research

Self Cite

137

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In the 1920s, Ronald Fisher developed the theory behind the p value and Jerzy Neyman and Egon Pearson developed the theory of hypothesis testing. These distinct theories have provided researchers important quantitative tools to confirm or refute their hypotheses. The p value is the probability to obtain an effect equal to or more extreme than the one observed presuming the null hypothesis of no effect is true; it gives researchers a measure of the strength of evidence against the null hypothesis. As commonly used, investigators will select a threshold p value below which they will reject the null hypothesis. The theory of hypothesis testing allows researchers to reject a null hypothesis in favor of an alternative hypothesis of some effect. As commonly used, investigators choose Type I error (rejecting the null hypothesis when it is true) and Type II error (accepting the null hypothesis when it is false) levels and determine some critical region. If the test statistic falls into that critical region, the null hypothesis is rejected in favor of the alternative hypothesis. Despite similarities between the two, the p value and the theory of hypothesis testing are different theories that often are misunderstood and confused, leading researchers to improper conclusions. Perhaps the most common misconception is to consider the p value as the probability that the null hypothesis is true rather than the probability of obtaining the difference observed, or one that is more extreme, considering the null is true. Another concern is the risk that an important proportion of statistically significant results are falsely significant. Researchers should have a minimum understanding of these two theories so that they are better able to plan, conduct, interpret, and report scientific experiments.

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Section: Implications For Researchmentioning

confidence: 99%

P Value and the Theory of Hypothesis Testing: An Explanation for New Researchers

Biau

Jolles

Porcher

2010

Clinical Orthopaedics &Amp; Related Research

Self Cite

137

View full text Add to dashboard Cite

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“…Also, a larger sample size results in more precision of the parameters being estimated thus resulting in more power as the estimates are more likely to be closer to the true values in the target population. (A more-detailed article by Biau et al [1] discusses the relationships between power and sample size along with examples. )…”

Section: Discussionmentioning

confidence: 99%

In Brief: Statistics in Brief: Statistical Power: What Is It and When Should It Be Used?

Dorey

2011

Clinical Orthopaedics &Amp; Related Research

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“…The power analysis according to Biau et al [4] was based on the biomechanical measures and results of Gardner et al [15]. The key variable of interest was defined as the posterior compression force in the plane of the pelvic ring.…”

Section: Methodsmentioning

confidence: 99%

Can a Modified Anterior External Fixator Provide Posterior Compression of AP Compression Type III Pelvic Injuries?

Sellei

Schandelmaier

Kobbe

et al. 2013

Clinical Orthopaedics &Amp; Related Research

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Background Current anterior fixators can close a disrupted anterior pelvic ring. However, these anterior constructs cannot create posterior compressive forces across the sacroiliac joint. We explored whether a modified fixator could create such forces. Questions/purposes We determined whether (1) an anterior external fixator with a second anterior articulation (X-frame) would provide posterior pelvic compression and (2) full pin insertion would deliver higher posterior compressive forces than half pin insertion. Methods We simulated AP compression Type III instability with plastic pelvis models and tested the following conditions: (1) single-pin supraacetabular external fixator (SAEF) using half pin insertion (60 mm); (2) SAEF using full pin insertion (120 mm); (3) modified fixator with X-frame using half pin insertion; (4) modified fixator using full pin insertion; and (5) C-clamp. Standardized fracture compression in the anterior and posterior compartment was performed as in previous studies by Gardner. A forcesensitive sensor was placed in the symphysis and posterior pelvic ring before fracture reduction and the fractures were reduced. The symphyseal and sacroiliac compression loads of each application were measured. Results The SAEF exerted mean compressions of 13 N and 14 N to the posterior pelvic ring using half and full pin insertions, respectively. The modified fixator had mean posterior compressions of 174 N and 222 N with half and full pin insertions, respectively. C-clamp application exerted a mean posterior load of 407 N. Conclusions Posterior compression on the pelvis was improved using an X-frame as an anterior fixation device in a synthetic pelvic fracture model. Clinical Relevance This additive device may improve the initial anterior and posterior stability in the acute management of unstable and life-threatening pelvic ring injuries.

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Statistics in Brief: The Importance of Sample Size in the Planning and Interpretation of Medical Research

Abstract: The

Cited by 292 publications

References 27 publications

P Value and the Theory of Hypothesis Testing: An Explanation for New Researchers

P Value and the Theory of Hypothesis Testing: An Explanation for New Researchers

In Brief: Statistics in Brief: Statistical Power: What Is It and When Should It Be Used?

Can a Modified Anterior External Fixator Provide Posterior Compression of AP Compression Type III Pelvic Injuries?

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