scholarly journals Conditional and Unconditional Tests (and Sample Size) Based on Multiple Comparisons for Stratified 2 × 2 Tables

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
A. Martín Andrés ◽  
I. Herranz Tejedor ◽  
M. Álvarez Hernández
Keyword(s):  
Sample Size ◽  
Sample Size Calculation ◽  
Multiple Comparisons ◽  
Calculation Methods ◽  
Global Test ◽  
Exact Test ◽  
Asymptotic Test ◽  
Chi Squared ◽  
Haenszel Test ◽  
Mc Method

The Mantel-Haenszel test is the most frequent asymptotic test used for analyzing stratified 2×2 tables. Its exact alternative is the test of Birch, which has recently been reconsidered by Jung. Both tests have a conditional origin: Pearson’s chi-squared test and Fisher’s exact test, respectively. But both tests have the same drawback that the result of global test (the stratified test) may not be compatible with the result of individual tests (the test for each stratum). In this paper, we propose to carry out the global test using a multiple comparisons method (MC method) which does not have this disadvantage. By refining the method (MCB method) an alternative to the Mantel-Haenszel and Birch tests may be obtained. The new MC and MCB methods have the advantage that they may be applied from an unconditional view, a methodology which until now has not been applied to this problem. We also propose some sample size calculation methods.

On powerful exact nonrandomized tests for the Poisson two-sample setting

2020 ◽  
Vol 29 (9) ◽  
pp. 2538-2553
Author(s):  
Stefan Wellek
Keyword(s):  
Sample Size ◽  
Test Procedure ◽  
Sample Size Calculation ◽  
Computational Procedure ◽  
Approximate Methods ◽  
Exact Test ◽  
Population Means ◽  
Specific Alternative ◽  
Conditional Tests ◽  
Natural Target

In the case of two independent samples from Poisson distributions, the natural target parameter for hypothesis testing is the ratio of the two population means. The conditional tests which have been derived for this class of problems already in the 1940s are well known to be optimal in terms of power only when randomized decisions between hypotheses are admitted at the boundary of the respective rejection regions. The major objective of this contribution is to show how the approach used by Boschloo in 1970 for constructing a powerful nonrandomized version of Fisher’s exact test for hypotheses about the odds ratio between two binomial parameters can successfully be adapted for the Poisson case. The resulting procedure, which we propose to term Poisson-Boschloo test, depends on some cutoff for the observed total number of events, the variable upon which conditioning has to be done. We show that for any fixed specific alternative, this cutoff can be chosen in such a way that the resulting nonrandomized test falls short in power of the randomized UMPU test only by a negligible amount. Thus, sample size calculation for the Poisson-Boschloo test can be carried out nearly exactly by means of the same computational procedure as has to be used for the randomized UMPU test. Since the power of the latter is accessible to elementary computational tools, this result makes approximate methods of sample size calculation for the Poisson-Boschloo test dispensable. It is furthermore shown how the construction of a Poisson-Boschloo type test extends to the case that interest is in establishing equivalence in the strict, two-sided sense rather than noninferiority. Although proceeding to two-sided equivalence considerably complicates the construction, comparing the resulting test procedure in terms of power with the exact randomized UMPU test leads essentially to the same conclusions as in the noninferiority case.

Impact of the p-Value Threshold on Interpretation of Trial Outcomes in Obstetrics and Gynecology

2021 ◽  
Author(s):  
Ann M. Bruno ◽  
Ashley E. Shea ◽  
Brett D. Einerson ◽  
Torri D. Metz ◽  
Amanda A. Allshouse ◽  
...  
Keyword(s):  
Sample Size ◽  
Primary Outcome ◽  
A Priori ◽  
Sample Size Calculation ◽  
P Value ◽  
Chi Square ◽  
Level Of Evidence ◽  
Exact Test ◽  
Manual Search ◽  
Significance Threshold

Objective Randomized controlled trials (RCTs) are considered the highest level of evidence to inform clinical practice. However, the reproducibility crisis has raised concerns about the scientific rigor of published RCT findings. Some advocate for a lower p-value threshold. We aimed to review published OB/Gyn topical RCTs in three representative OB/Gyn journals and three high impact non-OB/Gyn journals to determine if their interpretations would change with adoption of a p-value threshold for significance of 0.005. Secondarily, we evaluated if there were differences in methodologic characteristics between those that did and did not lose significance. Study Design A manual search was performed to identify all OB/Gyn RCTs published in the selected journals between July 2017 and June 2019. Data were collected on primary outcome(s), methodology, and p-values. We determined the proportion of primary outcomes that would remain statistically significant with adoption of a p-value significance threshold of 0.005 versus be reinterpreted as “suggestive” (defined as p-value between 0.005 and 0.05). Chi-square or Fisher's exact test were used to compare study characteristics. Results Overall, 202 RCTs met inclusion criteria; 52% in obstetrics and 48% in gynecology. Of 90 studies considered significant with p <0.05 at the time of publication, 54.4% (n = 49) would maintain significant (p < 0.005), while 45.6% (n = 41) would become suggestive using the lower threshold. Most RCTs utilized a single (90.1%) versus composite (8.9%) primary outcome type, used an intent-to-treat analysis (73.3%), and studied a drug intervention (46.5%). Methodologically, 23.7% did not prespecify analysis type, 28.2% did not meet the pre-determined sample size, and 9.4% did not report an a priori sample size calculation. Studies maintaining significance were more likely to be international and report a funding source. Conclusion Adopting a p-value significance threshold of 0.005 would require reinterpretation of almost half of RCT results in the OB/Gyn literature. Highly variable methodological quality was identified. Key Points

A cool modality to restore sinus rhythm

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
O Yasin ◽  
A Sugrue ◽  
M Van Zyl ◽  
A Ladejobi ◽  
J Tri ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Body Temperature ◽  
Sinus Rhythm ◽  
Animal Experiments ◽  
Funding Source ◽  
Atrial Pacing ◽  
Exact Test ◽  
Chi Squared ◽  
Cool Device ◽  
Atrial Defibrillation

Abstract Background Slowing electrical conduction by cooling the myocardium can be used for defibrillation. We previously demonstrated the efficacy of a small cold device placed in oblique sinus (OS) in terminating atrial fibrillation (AF). However, the parameters needed to achieve effective atrial defibrillation are unknown. Purpose Assess effect of the size of cooled myocardium on frequency of AF termination in acute canine animal models. Methods Sternotomy was performed under general anesthesia in 10 acute canine experiments. AF was induced using rapid atrial pacing and intra-myocardial epinephrine and acetylcholine injections. Once AF sustained for at least 30s, either a cool (7–9°C) or placebo (body temperature) device was placed in the OS. Four device sizes were tested; ½X½, ¾X¾, and 1X1 inch devices and two ¾X¾ inch devices placed side by side simultaneously. Time to AF termination was recorded. Chi-squared or Fisher's exact test were used to compare the frequency of arrhythmia termination with cooling versus placebo. Results A total of 166 applications were performed (89 cool vs 77 placebo) in 10 animal experiments. Overall, AF terminated in 82% of the cooling applications vs. 67.5% of placebo (P=0.03, Figure 1). For the ½X½ inch device 88% of cold applications restored sinus rhythm vs. 63.6% for placebo (P=0.05). The frequency of sinus restoration for cold ¾X¾, 1X1 and two ¾X¾ side by side devices was 86.7%, 83.3% and 70% respectively. Time to sinus restoration when achieved was within three minutes was also not significantly changed. Conclusion Placing a cool device in the oblique sinus can terminate AF and efficacy is not affected by the size of device. Funding Acknowledgement Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): MediCool Technologies

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