A note on the conservativeness of the confidence interval approach for the selection of non‐inferiority margin in the two‐arm active‐control trial

2008 ◽  
Vol 27 (19) ◽  
pp. 3732-3742 ◽  
Author(s):  
Abdul J. Sankoh
Keyword(s):  
Confidence Interval ◽  
Active Control ◽  
Interval Approach ◽  
Selection Of

scholarly journals Confidence interval approach for evaluating bias in laboratory methods

1988 ◽  
Vol 10 (3) ◽  
pp. 144-146 ◽  
Author(s):  
K. F. Yee
Keyword(s):  
Confidence Interval ◽  
Statistical Tests ◽  
Laboratory Methods ◽  
Mean Values ◽  
Practical Concern ◽  
Alternative Approach ◽  
Interval Approach ◽  
Significant Difference ◽  
The Mean

A statistically significant difference in mean values between two laboratory quantitation methods is interpreted as a bias. Sometimes such a difference is so minute that it does not constitute any practical concern. An alternative approach is to test statistically whether the two methods are close enough, not for equality. This is to look at the confidence interval of the mean method difference and does not entail any additional statistical tests.

scholarly journals Non-inferiority test for a continuous variable with a flexible margin in an active controlled trial : An application to the "Stratall ANRS 12110 / ESTHER" trial

2020 ◽  
Author(s):  
Arsene Sandie ◽  
Nicholas Molinari ◽  
Anthony Wanjoya ◽  
Charles Kouanfack ◽  
Christian Laurent ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Active Control ◽  
Error Rate ◽  
Type I Error ◽  
Clinical Monitoring ◽  
Small Scale ◽  
Type I ◽  
Test Procedures ◽  
Power Estimate ◽  
Control Intervention

Abstract Background: The non-inferiority trials are becoming increasingly popular in public health and clinical research. The choice of the non-inferiority margin is the cornerstone of the non-inferiority trial. When the effect of active control intervention is unknown, it can be interesting to choose the non-inferiority margin as a function of the active control intervention effect. In this case, the uncertainty surrounding the non-inferiority margin should be accounted for in statistical tests. In this work, we explored how to perform the non-inferiority test with a flexible margin for continuous endpoint.Methods: It was proposed in this study two procedures for the non-inferiority test with a flexible margin for the continuous endpoint. The proposed test procedures are based on test statistic and confidence interval approach. Simulations have been used to assess the performances and properties of the proposed test procedures. An application was done on clinical real data, which the purpose was to assess the efficacy of clinical monitoring alone versus laboratory and clinical monitoring in HIV-infected adult patients.Results: Basically, the two proposed test procedures have good properties. In the test based on a statistic, the actual type 1 error rate estimate is approximatively equal to the nominal value. It has been found that the confidence interval level determines approximately the level of significance. The 80%, 90%, and 95%one-sided confidence interval levels led approximately to a type I error of 10%, 5% and 2.5% respectively. The power estimate was almost 100% for two proposed tests, except for the small scale values of the reference treatment where the power was relatively low when the sample sizes were small.Conclusions: Based on type I error rate and power estimates, the proposed non-inferiority hypothesis test procedures have good performance and are applicable in practice.Trial registration: The trial data used in this study was from the ”Stratall ANRS 12110 / ESTHER”, registered with ClinicalTrials.gov, number NCT00301561. Date : March 13, 2006, url : https://clinicaltrials.gov/ct2/show/NCT00301561.

Selection of weights for a weighted regression of tree volume

1986 ◽  
Vol 16 (3) ◽  
pp. 671-673 ◽  
Author(s):  
C. H. Meng ◽  
W. Y. Tsai
Keyword(s):  
Confidence Interval ◽  
Likelihood Function ◽  
Weighted Least Squares ◽  
Tree Height ◽  
Regression Equations ◽  
Tree Diameter ◽  
A Value ◽  
Log Likelihood ◽  
Homogeneity Of Variance ◽  
Selection Of

The construction of regression equations for predicting tree volumes requires the assumption of homogeneity of variance that can be achieved by the method of weighted least squares. Some of the weights have the form (1/DλH)2 or (1/Dλ)2 (where D represents tree diameter at breast height and H represents tree height). Traditionally, λ has been assigned a value of 2. This paper suggests a method to estimate the exponent λ. This is accomplished by finding a maximum log likelihood function for a transformed tree volume regression equation. A proper value of λ is chosen within the confidence interval of λ. The confidence interval is established from the maximum log likelihood function.

scholarly journals Confidence interval approach to feature re-weighting

2008 ◽  
Vol 40 (3) ◽  
pp. 385-407 ◽  
Author(s):  
Robert S. Lee ◽  
Chin-Wan Chung ◽  
Seok-Lyong Lee ◽  
Sang-Hee Kim
Keyword(s):  
Confidence Interval ◽  
Interval Approach

α+-thalassemia protects African children from severe malaria

Blood ◽  
2004 ◽  
Vol 104 (7) ◽  
pp. 2003-2006 ◽  
Author(s):  
Frank P. Mockenhaupt ◽  
Stephan Ehrhardt ◽  
Sabine Gellert ◽  
Rowland N. Otchwemah ◽  
Ekkehart Dietz ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Natural Selection ◽  
Confidence Interval ◽  
Severe Malaria ◽  
High Frequency ◽  
Odds Ratio ◽  
Case Control Study ◽  
Case Control ◽  
Control Study ◽  
Selection Of

Abstract The high frequency of α+-thalassemia in malaria-endemic regions may reflect natural selection due to protection from potentially fatal severe malaria. In Africa, bearing 90% of global malaria morbidity and mortality, this has not yet been observed. We tested this hypothesis in an unmatched case-control study among 301 Ghanaian children with severe malaria and 2107 controls (62% parasitemic). In control children, α+-thalassemia affected neither prevalence nor density of Plasmodium falciparum. However, heterozygous α+-thalassemia was observed in 32.6% of controls but in only 26.2% of cases (odds ratio [OR], 0.74; 95% confidence interval [CI], 0.56-0.98). Protection against severe malaria was found to be pronounced comparing severe malaria patients with parasitemic controls (adjusted OR in children < 5 years of age, 0.52; 95% CI, 0.34-0.78) and to wane with age. No protective effect was discernible for homozygous children. Our findings provide evidence for natural selection of α+-thalassemia in Africa due to protection from severe malaria.

DYNAMICS AND ACTIVE CONTROL OF MOTION OF A DRIVEN MULTI-LIMIT-CYCLE VAN DER POL OSCILLATOR

2007 ◽  
Vol 17 (04) ◽  
pp. 1343-1354 ◽  
Author(s):  
R. YAMAPI ◽  
B. R. NANA NBENDJO ◽  
H. G. ENJIEU KADJI
Keyword(s):  
Limit Cycle ◽  
Active Control ◽  
Coupling Parameter ◽  
Van Der Pol Oscillator ◽  
External Excitation ◽  
Van Der Pol ◽  
Chaotic Vibrations ◽  
Van Der Pol Model ◽  
Nonautonomous Case ◽  
Selection Of

This paper deals with the dynamics and active control of a driven multi-limit-cycle Van der Pol oscillator. The amplitude of the oscillatory states both in the autonomous and nonautonomous case are derived. The interaction between the amplitudes of the external excitation and the limit-cycles are also analyzed. The domain of the admissible values on the amplitude for the external excitation is found. The effects of the control parameter on the behavior of a driven multi-limit-cycle Van der Pol model are analyzed and it appears that with the appropriate selection of the coupling parameter, the quenching of chaotic vibrations takes place.

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