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Smallest Sample Size (smallest + sample_size)
Selected AbstractsPotential outcome measures and trial design issues for multiple system atrophy,MOVEMENT DISORDERS, Issue 16 2007Susanne May PhD Abstract Multiple system atrophy (MSA) is a neurodegenerative disorder exhibiting a combination of parkinsonism, cerebellar ataxia, and autonomic failure. A disease-specific scale, the Unified Multiple System Atrophy Rating Scale (UMSARS), has been developed and validated to measure progression of MSA, but its use as an outcome measure for therapeutic trials has not been evaluated. On the basis of twelve months of follow-up from an observational study of 67 patients with probable MSA, we evaluated three disease-specific scores: Activities of Daily Living, Motor Examination, and a combined score from the UMSARS and two general health scores, the Physical Health and Mental Health scores of the SF-36 health survey, for their use as outcome measures in a therapeutic trial. We discuss related design issues and provide sample size estimates. Scores based on the disease-specific UMSARS seemed to be equal or superior to scores based on the SF-36 health survey. They appeared to capture disease progression, were well correlated and required the smallest sample size. The UMSARS Motor Examination score exhibited the most favorable characteristics as an outcome measure for a therapeutic trial in MSA with 1 year of follow-up. © 2007 Movement Disorder Society [source] Corticosteroid Treatment for Idiopathic Facial Nerve Paralysis: A Meta-analysis,THE LARYNGOSCOPE, Issue 3 2000Mitchell Jay Ramsey CPT Abstract Objective A meta-analysis was designed to evaluate facial recovery in patients with complete idiopathic facial nerve paralysis (IFNP) by comparing outcomes of those treated with corticosteroid therapy with outcomes of those treated with placebo or no treatment. Study Design Meta-analysis of prospective trials evaluating corticosteroid therapy for idiopathic facial nerve paralysis. Methods A protocol was followed outlining methods for trial selection, data extraction, and statistical analysis. A MEDLINE search of the English language literature was performed to identify clinical trials evaluating steroid treatment of IFNP. Three independent observers used an eight-point analysis to determine inclusion criteria. Data analysis was limited to individuals with clinically complete IFNP. The endpoints measured were clinically complete or incomplete facial motor recovery. Effect magnitude and significance were evaluated by calculating the rate difference and Fisher's Exact Test P value. Pooled analysis was performed with a random effects model. Results Forty-seven trials were identified. Of those, 27 were prospective and 20 retrospective. Three prospective trials met the inclusion criteria. Tests of heterogeneity indicate the trial with the smallest sample size (RD = ,0.19; 95% CI, ,0.58,0.20), to be an outlier. It was excluded from the final analysis. Analyses of data from the remaining two studies indicate corticosteroid treatment improves complete facial motor recovery for individuals with complete IFNP. Rate difference demonstrates a 17% (99% CI, 0.01,0.32) improvement in clinically complete recovery for the treatment group based on the random effects model. Conclusions Corticosteroid treatment provides a clinically and statistically significant improvement in recovery of function in complete IFNP. [source] Sequential design in quality control and validation of land cover databasesAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 2 2009Elisabetta Carfagna Abstract We have faced the problem of evaluating the quality of land cover databases produced through photo-interpretation of remote-sensing data according to a legend of land cover types. First, we have considered the quality control, that is, the comparison of a land cover database with the result of the photo-interpretation made by a more expert photo-interpreter, on a sample of the polygons. Then we have analysed the problem of validation, that is, the check of the photo-interpretation through a ground survey. We have used the percentage of area correctly photo-interpreted as a quality measure. Since the kind of land cover type and the size of the polygons affect the probability of making mistakes in the photo-interpretation, we stratify the polygons according to two variables: the land cover type of the photo-interpretation and the size of the polygons. We have proposed an adaptive sequential procedure with permanent random numbers in which the sample size per stratum is dependent on the previously selected units but the sample selection is not, and the stopping rule is not based on the estimates of the quality parameter. We have proved that this quality control and validation procedure allows unbiased and efficient estimates of the quality parameters and allows reaching high precision of estimates with the smallest sample size. Copyright © 2009 John Wiley & Sons, Ltd. [source] Above- versus below-ground competitive effects and responses of a guild of temperate tree speciesJOURNAL OF ECOLOGY, Issue 1 2009K. David Coates Summary 1The neutral theory debate has highlighted the scarcity of robust empirical estimates of the magnitude of competitive effects and responses within guilds of co-occurring tree species. Our analysis quantifies the relative magnitude of all possible pairwise competitive interactions within a guild of nine co-occurring tree species in temperate forests of northern, interior British Columbia, and explicitly partitions the competitive effects of neighbours into the effects of shading versus the residual effects of ,crowding', assumed to reflect below-ground competition. 2Models that treated neighbours as equivalent in their competitive effects were the most parsimonious for the five species with the smallest sample sizes. For the remaining species (samples sizes of > 150 individuals), the best models estimated separate competition coefficients for all nine species of neighbours. We take this as evidence that species do indeed differ in their competitive effects, but that there can be a minimum sample size required to discriminate between them. 3There was a strong size-dependency in potential growth. Six species showed an optimal growth at a size between 5 and 20 cm diameter. Potential growth declined moderately to strongly as diameter increased. Sensitivity to crowding varied as a function of tree size for five of the nine species; however, this response was not consistent by tree species. 4The magnitude of reduction in growth due to crowding was greater on average than the reduction in growth due to shading, except for the two least shade tolerant conifers. Sensitivity to shading among the conifer species was correlated with their shade tolerance. 5The per capita effects of crowding by different species of neighbours varied widely. A large number of the estimated pairwise per capita competition coefficients were very low. The relative magnitude of the strength of intra- versus interspecific competition also varied widely among the tree species. 6Synthesis. Model selection techniques effectively separated above- and below-ground competition in complex forests, and allowed us to assess differences among species in competitive effects and responses. While below-ground effects were strong, they were due to proximity of neighbours from a very specific (and small) subset of strong competitors within the guild. Response to crowding varied with tree size but the nature of the relationship varied widely among the species. [source] Standardizing Emergency Department,based Migraine Research: An Analysis of Commonly Used Clinical Trial Outcome MeasuresACADEMIC EMERGENCY MEDICINE, Issue 1 2010Benjamin W. Friedman MD Abstract Objectives:, Although many high-quality migraine clinical trials have been performed in the emergency department (ED) setting, almost as many different primary outcome measures have been used, making data aggregation and meta-analysis difficult. The authors assessed commonly used migraine trial outcomes in two ways. First, the authors examined the association of each commonly used outcome versus the following patient-centered variable: the research subject's wish, when asked 24 hours after investigational medication administration, to receive the same medication the next time they presented to an ED with migraine ("would take again"). This variable was chosen as the criterion standard because it provides a simple, dichotomous, clinically sensible outcome, which allows migraineurs to factor important intangibles of efficacy and adverse effects of treatment into an overall assessment of care. The second part of the analysis assessed how sensitive to true efficacy each outcome measure was by calculating sample size requirements based on results observed in previously conducted clinical trials. Methods:, This was a secondary analysis of data previously collected in four ED-based migraine randomized trials performed between 2003 and 2007. In each of these trials, subjects were asked 24 hours after administration of an investigational medication whether or not they would want to receive the same medication the next time they came to the ED with a migraine. Odds ratios (ORs) with 95% confidence intervals (CIs), adjusted for sex and medication received, were calculated as measures of association between the most commonly used outcome measures and "would take again." The sensitivity of each outcome measure to treatment efficacy was determined by calculating the sample size that would be required to detect a statistically significant result using estimates of that outcome obtained in two clinical trials. Results:, Data from 378 subjects were used for this analysis. Adjusted ORs for association of "would take again" and other commonly used primary headache outcomes are as follows: achieving a pain-free state by 2 hours, OR = 3.1 (95% CI = 1.8 to 5.4); sustained pain-free status, OR = 4.5 (95% CI = 1.9 to 11.0); and no need for rescue medication, OR = 3.7 (95% CI = 2.1 to 6.6). An improvement on a standardized 11-point pain scale of ,33% had an adjusted OR = 5.2 (95% CI = 2.2 to 12.4). The best performing alternate outcome, ,33% improvement, correctly classified 288 subjects and misclassified 77 subjects when compared to "would take again." At least 33% improvement and pain-free by 2 hours required the smallest sample sizes, while sustained pain-free and "would take again" required many more subjects. Conclusions:, "Would take again" was associated with all migraine outcome measures we examined. No individual outcome was more closely associated with "would take again" than any other. Even the best-performing alternate outcome misclassified more than 20% of subjects. However, sample sizes based on "would take again" tended to be larger than other outcome measures. On the basis of these findings and this outcome measure's inherent patient-centered focus, "would take again," included as a secondary outcome in all ED migraine trials, is proposed. ACADEMIC EMERGENCY MEDICINE 2010; 17:72,79 © 2010 by the Society for Academic Emergency Medicine [source] | ||||||||||