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At least 55 records · Page 3Linked to original sources
PubMed2006

Reproducibility of time at or near VO2max during intermittent treadmill running.

The purpose of this study was to determine the reproducibility of time at or above 90 % (t (90 % )VO (2max)) and 95 % (t (95 % )VO (2max)) maximal oxygen uptake during an intermittent treadmill run to exhaustion. Twenty-two distance runners (age 38.0 +/- 7.1 yrs) performed two identical incremental and two identical intermittent tests on four separate days. Respiratory exchange was measured continuously throughout each test by an automated open-circuit gas analysis system. The incremental test consisted of increases in treadmill speed every minute until volitional exhaustion. The highest averaged 30-s oxygen uptake (VO (2)) value was defined as VO (2max) and the minimum speed that elicited VO (2max) was defined as vVO (2max). The intermittent test consisted of 30-s work intervals ran at 105 % vVO (2max) interspersed by 30-s relief intervals ran at 60 % vVO (2max) and was continued until volitional exhaustion. The time that VO (2) was at or above 90 % and 95 % of the mean maximum values elicited during the two previous incremental tests was determined for the intermittent tests. The mean t (95 % )VO (2max) was 232 (SD 174) s and 244 (SD 195) s and the mean t (90 % )VO (2max) was 480 (SD 220) s and 488 (SD 252) s, for trial 1 and trial 2, respectively. Reproducibility statistics for t (95 % )VO (2max) and t (90 % )VO (2max), respectively, were: 95 % limits of agreement 12 +/- 227 s and 8 +/- 328 s; coefficient of variation 34.5 % and 24.5 %; and intraclass correlation coefficient 0.80 and 0.75. Statistical power analysis indicated that this level of reproducibility would allow mean differences of 15 - 20 % between intermittent training protocols to attain statistical significance in future experimental research, with sample sizes probably within the resources of most researchers.

Adult↗
PubMed2003

Estimating three-dimensional spinal repositioning error: the impact of range, posture, and number of trials.

STUDY DESIGN: Spinal repositioning sense was tested in normal subjects using a balanced within-subject study design. OBJECTIVES: The study had three objectives: first, to document the number of trials required to derive a representative value of accuracy and precision in spinal repositioning; second, to document the effects of range on spinal repositioning sense; and finally, to document the effect of different lower limb postures on the repositioning performance. SUMMARY OF BACKGROUND DATA: Joint position sense and kinesthesia play an important role in the control of normal movement of the spine. This has important implications for the diagnosis and assessments of specific movement disorders in individuals with spinal pain syndromes. The literature is varied in methods and results in assessing spinal repositioning sense. For some studies, the inability to determine effects for range or differences between patients with low back pain and normal control subjects may be related to the fact that too few trials were performed to detect a statistical difference. METHODS: Twenty-three subjects were tested in standing on a repositioning task for spinal position sense. After a familiarization period, each subject performed 10 matching trials in three ranges (20%, 50%, and 80% of available range) during spinal flexion. The flexion task was performed with knees fully extended, with knees partly flexed, and with the pelvis rotated at 45 degrees to incorporate an asymmetric flexion rotation movement pattern. The three-dimensional coordinates of the repositioning tasks were used to determine accuracy (mean and median of trials) and precision (variable error-standard deviation of trials). The coefficient of variation and statistical power analysis using variables derived from progressively larger numbers of trials were examined. Analysis of variance was used to detect differences for the three ranges and three postures. RESULTS: After the familiarization period, no learning effect was demonstrated across trials. The coefficient of variation and statistical power for the accuracy and precision tended to stabilize after six trials. Using derived variables from six trials, there was a statistically significant range effect. Accuracy in the inner range was worse than that in the outer range (P < 0.05). There was little evidence of a range effect for precision. Posture had little overall impact. Trunk flexion with the knees flexed improved three-dimensional accuracy in the middle range compared with accuracy with the knees extended and during the flexion rotation task. CONCLUSIONS: It was concluded that increasing the number of trials increases the statistical power and stability of the derived variables. In normal subjects, the accuracy of trunk flexion repositioning improves as one moves further into range.

Adult↗
PubMed1988

Effect of drawing blood specimens proximal to an in-place but discontinued intravenous solution. Can blood be drawn above the site of a shut-off i.v.?

To assess the effects of drawing blood specimens from a site proximal to an intravenous (IV) infusion line, 24 volunteers were infused with approximately 30 mL of 5% (w/v) dextrose in 0.9% (w/v) NaCl solution. Specimens were drawn proximal to the IV line, while the solution was infusing, and at 1, 2, and 3 minutes after discontinuance of the infusion and assayed for glucose, sodium, chloride, and red blood cell (RBC) count. Control samples were obtained simultaneously from the opposite arm to determine any residual or dilutional effects from the infusing solution. Statistical analysis using the paired sample t-test showed no significant difference of RBCs between arms at or beyond 1 minute. Statistical power analysis reveals that there is a 95% level of certainty that there is less than 1% dilution of the test arm specimen. Analysis of sodium and chloride levels showed no contamination of the test arm specimen at 1 minute, but glucose concentrations still showed an average elevation over control of 5% at 3 minutes. The authors concluded that the drawing of blood specimens proximal to an IV infusion, 3 minutes after its discontinuance, has a clinically negligable dilutional effect but substances present at relatively high levels in the infused solution may still be detected.

Adult↗
PubMed2005

Behavior and the limits of genomic plasticity: power and replicability in microarray analysis of honeybee brains.

Transcription is slow relative to many post-transcriptional processes in the brain. Using the rich system of division of labor in the honeybee (Apis mellifera), we found extreme differences in the extent to which behavioral occupations of different durations were associated with gene-expression differences in the brain. Nursing and foraging, occupations lasting > 1 week, were associated with significant expression differences for nearly one-quarter of the genes tested (1208 of 5563 cDNAs tested; P < 0.01, anova), consistent with previous results. In contrast, transitional occupations, performed for 1-2 days after nursing and before the onset of foraging, were associated with either no differences (guards vs. undertakers; 19 cDNAs, fewer than the expectation of 56 false-positives) or few differences (comb builders vs. guards and undertakers; 248 cDNAs), but extensive differences relative to both nursing and foraging (> 500 cDNAs, all contrasts). Statistical power analysis indicated that expression differences of two-, 1.5- and 1.25-fold should have been detected in 100, 92 and 37% of cases, respectively. Replication of previous results at these magnitudes was 95, 71 and 51%, with no genes showing differences in the opposite direction. These results indicate that behavioral plasticity over different time-scales may be associated with substantial differences in the extent of genomic plasticity in the brain.

Animals↗
PubMed1986

Determination of bioequivalence of psychotropic drugs and concerns involving product interchange.

There is a growing debate among researchers and practitioners concerning the validity of the Food and Drug Administration (FDA) standards for establishing generic interchange through assignment of "therapeutically equivalent" designations for noninnovator or generic drugs. This debate has particular significance for psychotropic drugs which are used in the management of patients with severely debilitating mental diseases. Thus, the controversy primarily focuses on the appropriateness of using the FDA's therapeutic equivalence designation as a criterion for interchange. This is particularly important in light of the lack of well-defined standards for bioequivalence studies and in view of the effect of mandatory substitution laws and financial incentives that encourage generic dispensing that can lead to frequent and indiscriminate interchange among multiple generic brands. Specific concerns include the validity of assay techniques for drug in biologic fluids, statistical power analysis, the appropriateness of the "70/70 rule," and the relevance of studies carried out in healthy normal volunteers in the determination of bioequivalence.

Antipsychotic Agents↗
PubMed1978

Statistical power in physical anthropology: a technical report.

A statistical power analysis of The American Journal of Physical Anthropology (Volume 44, 1976) was conducted. Twenty-five articles, which included 3,304 major significance tests, constituted the final sample. Resultant power estimates of 0.38, 0.62, and 0.81, corresponding to small, medium, and large population effects respectively, were obtained. Although the medium effect size estimate falls short of the recommended 0.80 level, the statistical power of physical anthropological research fares well relative to several of the social scientific fields of inquiry.

Anthropology, Physical↗
PubMed1994

Doppler velocimetry of maternal renal interlobar arteries in pregnancy-induced hypertension.

OBJECTIVES: To evaluate whether Doppler velocimetry of maternal renal interlobar arteries is altered in patients with hypertensive disorders of pregnancy (PIH). METHODS: Flow velocity waveforms (FVWs) were obtained, by means of color and pulsed Doppler ultrasound, from the renal artery and two interlobar arteries in the right kidney of 46 normal pregnant women and 10 patients with PIH between 20 and 39 weeks' gestation. Statistical analyses of resistance indices (RI) were performed by regression analysis, paired and unpaired t-tests. RESULTS: RI values of renal and interlobar arteries in normal patients did not change significantly with gestational age. Interlobar arteries had significantly lower RI values than corresponding main renal arteries (T = 3.88, P < 0.001). No significant differences in FVWs of renal (T = 1.86, P = 0.068) and interlobar arteries (T = 0.85, P = 0.399) were found between normal and hypertensive patients. A statistical power analysis confirmed that our sample size was sufficient to detect a difference in RI of 0.10, with alpha = 0.05 and beta = 0.80. CONCLUSIONS: FVWs of the renal and interlobar arteries are not altered in patients with mild PIH.

Blood Flow Velocity↗
PubMed1998

Statistical methodology: IV. Analysis of variance, analysis of covariance, and multivariate analysis of variance.

Medical research frequently involves the statistical comparison of >2 groups, often using data obtained through the application of complex experimental designs. Fortunately, inferential statistical methodologies exist to address these situations. Analysis of variance (ANOVA) in its many forms is used to simultaneously test the equality of all groups in a study. One-way (with 1 independent variable), 2-way (with 2 independent variables), and repeated-measures (patients serve as their own controls) ANOVAs are forms of this technique. Each form has been developed to analyze data from a specific experimental design. Analysis of covariance (ANCOVA) allows the researcher to control for confounding variables that may influence the response of the dependent variable. Finally, multivariate analysis of variance (MANOVA) evaluates the simultaneous responses of multiple dependent variables to > or = 1 independent variable. Whereas ANOVA is the correct alternative to statistically inappropriate multiple t-tests, MANOVA is the correct alternative to statistically inappropriate multiple univariate ANOVA calculations. Use of each of these statistical methods requires an appropriate experimental design and data meeting a number of assumptions. When used properly, each of these methods provides a powerful statistical analysis technique.

Analysis of Variance↗
PubMed2004

[What place for DNA microarray in inflammatory diseases?].

PURPOSE: DNA chip is a recently developed technique allowing analysis of thousands of genes at the same time in multiple biological samples. In few years it has become an obligatory step in massive gene expression study. The enormous quantity of results generated and the new way of thinking allowed make this kind of study a true revolution. KEY MESSAGE AND RECENT FACTS: The enormous discovery potential permitted by the accomplishment of multiple genomes sequencing and the advent of technologies allowing massive gene expression analyses have totally modified the diseases approach. Considering the obtainment of a real full picture of the transcriptional activity in an organ, tissue or cell is now legitimate. DNA microarray is obviously not the only technique allowing such type of analysis but it is without contest the technology which is the most popular and the one which has been recently the subject of the most important developments. It is certainly the technology which brought the main advances in tumour classification and discovery of new biomarkers. The first results based on this technology in inflammatory diseases have recently been reported. PERSPECTIVE AND PROJECTS: The optimal use of DNA microarrays will necessitate a powerful statistical analysis and an high quality biological experimentation. Strict standard and quality criteria are developing. Obviously, the DNA chips have a role to play in multifactorial inflammatory diseases mainly through their potential to bring new answers to diagnostic and pathophysiological problems. One potential development of the technique in such diseases will be the definition of disease specific gene profiles and the generation of chips allowing the detection of few targeted genes with all the known mutations of these genes. The correlation of global or targeted gene expression with clinical and pathological data will allow a new step forward in the understanding and taking care of inflammatory diseases.

Animals↗
PubMed1999

Behavioral science foundations of the Rorschach test: research and clinical applications.

Never without its critics, the Rorschach Test continues to be widely used in clinical settings. The test continues to be criticized vigorously. Rorschach critics appear to fall into two broad groups: those leveling valid methodological concerns about the test s behavioral science foundations and method critics who appear to deny the validity of the test on strictly a priori or theoretical considerations. Many critics do not appear to be acquainted with the extensive Rorschach research literature. The current paper provides an overview of several domains of applied and laboratory Rorschach behavioral science, including statistical power analysis, interobserver agreement and interrater reliability, Rorschach assessment of thought disorder, and emerging research linking Rorschach variables with diagnostic criteria from the DSM-IV, as a means of educating both adherents and detractors alike concerning the test s scientific track record and applicability to clinical assessment.

Behavioral Sciences↗
PubMed1993

Measuring male reproductive hormones for occupational field studies.

As part of our longitudinal study of unexposed workers, we drew blood samples and analyzed the individual endocrine profiles for 45 men. The blood collection was between 8 AM and 8 PM, and three blood samples were drawn 20 minutes apart on three occasions during the course of the study (June, October, and February). Serum concentrations of follicle-stimulating hormone, luteinizing hormone, testosterone, and prolactin were determined. A component of variance model was used to estimate variability between the 20-minute blood draws. Statistical power analysis using this component showed that three blood draws provide a marginal improvement over a single blood draw in detecting population shifts. Also, if the prospect of three blood draws reduces subject participation by 10 to 20%, the increase in power would be negated.

Adult↗
PubMedDate not supplied

A critique of Mody, Studdert-Kennedy, and Brady's "Speech perception deficits in poor readers: auditory processing or phonological coding?".

A 1997 article by Mody, Studdert-Kennedy, and Brady claimed that their studies constituted a critical test of two hypotheses concerning students with reading impairment: (a) that they experience speech-specific failure in phonological representation, and (b) they display general deficits in auditory temporal processing. From these studies, the authors concluded that their findings were consistent with the first hypothesis but were not in agreement with the second. A critical analysis of the Mody et al. article leads to the conclusion that it makes no contribution to that debate because (a) the children in the Poor reading group did not meet the accepted reading-impairment criterion of being delayed by at least 1 year in their reading skills, (b) there were severe violations of statistical assumptions, and (c) their conclusions were based on the failure to find significant differences, thus compelling them to accept the null hypothesis as proven, in the absence of any statistical power analysis.

Auditory Perceptual Disorders↗
PubMed2004

Sample size estimation: a glimpse beyond simple formulas.

Small increments in the complexity of clinical studies can readily take sample size estimation and statistical power analysis beyond the capabilities of simple mathematic formulas. In this article, the method of simulation is presented as a general technique with which sample size may be calculated for complex study designs. Applications of simulation for determining sample size requirements in studies involving correlated data and comparisons of receiver operating characteristic curves are discussed.

Clinical Trials as Topic↗
PubMed2001

Statistical power and effect sizes of clinical neuropsychology research.

Cohen, in a now classic paper on statistical power, reviewed articles in the 1960 issue of one psychology journal and determined that the majority of studies had less than a 50-50 chance of detecting an effect that truly exists in the population, and thus of obtaining statistically significant results. Such low statistical power, Cohen concluded, was largely due to inadequate sample sizes. Subsequent reviews of research published in other experimental psychology journals found similar results. We provide a statistical power analysis of clinical neuropsychological research by reviewing a representative sample of 66 articles from the Journal of Clinical and Experimental Neuropsychology, the Journal of the International Neuropsychology Society, and Neuropsychology. The results show inadequate power, similar to that for experimental research, when Cohen's criterion for effect size is used. However, the results are encouraging in also showing that the field of clinical neuropsychology deals with larger effect sizes than are usually observed in experimental psychology and that the reviewed clinical neuropsychology research does have adequate power to detect these larger effect sizes. This review also reveals a prevailing failure to heed Cohen's recommendations that researchers should routinely report a priori power analyses, effect sizes and confidence intervals, and conduct fewer statistical tests.

Data Interpretation, Statistical↗
PubMed2005

Preclinical assessment of HIV vaccines and microbicides by repeated low-dose virus challenges.

BACKGROUND: Trials in macaque models play an essential role in the evaluation of biomedical interventions that aim to prevent HIV infection, such as vaccines, microbicides, and systemic chemoprophylaxis. These trials are usually conducted with very high virus challenge doses that result in infection with certainty. However, these high challenge doses do not realistically reflect the low probability of HIV transmission in humans, and thus may rule out preventive interventions that could protect against "real life" exposures. The belief that experiments involving realistically low challenge doses require large numbers of animals has so far prevented the development of alternatives to using high challenge doses. METHODS AND FINDINGS: Using statistical power analysis, we investigate how many animals would be needed to conduct preclinical trials using low virus challenge doses. We show that experimental designs in which animals are repeatedly challenged with low doses do not require unfeasibly large numbers of animals to assess vaccine or microbicide success. CONCLUSION: Preclinical trials using repeated low-dose challenges represent a promising alternative approach to identify potential preventive interventions.

AIDS Vaccines↗
PubMed2002

More power to you: simple power calculations for treatment effects with one degree of freedom.

Although numerous computer programs for statistical power analysis are available, power is an under-used aspect of experimental analysis, perhaps because of the perceived difficulty of performing the necessary calculations or because existing computer software can be expensive or complicated to learn. For single-degree-of-freedom tests, however, it is possible to calculate power in a straightforward manner, using the t distribution. Because these calculations are based on t, they use easily understood and readily available quantities. These calculations can be performed with a desk calculator; we also present a simple-to-use program called MorePower that will perform the necessary calculations. The straightforward nature of the calculations potentially will enable more researchers to consider issues of power when planning and reporting their experiments.

Humans↗
PubMed2000

[Progress in the studies on the molecular genetics of schizophrenia].

Although population genetic studies have long confirmed the genetic vulnerability of schizophrenia,ongoing advances in molecular genetic technology and biostatistic analysis are only now making it possible to search for the susceptibility gene of the disease. This article reviewed some of the recent findings in this area: (1) The heritability of schizophrenia is estimated around 60%-80%. The phenotype differentiation is based on standard diagnostic scales and symptom rating scales. (2) The two main approaches to finding the genes that influence the disorder are now genomic scan and candidate gene detection. Affected sib-pair (ASP) method and transmission disequilibrium test(TDT) are considered promising analyses. (3) The positive candidate regions with some independent replicable reports concentrated on 6p, 22q and 8p. Positive findings of candidate gene research involved 5-HT2A receptor, DRD3, NT-3, etc. Further directions to identify the susceptibility genes include: Applying more precise instruments to define clinical phenotype of the disease. Application of proper biological markers such as electrophysiologic parameters and brain imaging will be a prospective approach. Using larger sample to increase statistic power and developing more powerful statistic analysis, and performing advanced molecular genetic technique such as DNA pooling, DNA chips, genomic mismatch scanning (GMS), representational difference analysis(RDA), comparative genomic hybridization(CGH) and two-dimensional DNA typing methods will also facilitate this research area to greater perspective.

Chromosome Aberrations↗
PubMed2006

Meniscus allograft survival in patients with moderate to severe unicompartmental arthritis: a 2- to 7-year follow-up.

PURPOSE: We present meniscus allograft survival data at least 2 years from surgery for 45 patients (47 allografts) with significant arthrosis to determine if the meniscus can survive in an arthritic joint. TYPE OF STUDY: Prospective, longitudinal survival study. METHODS: Data were collected for 31 men and 14 women, mean age 48 years (range, 14 to 69 years), with preoperative evidence of significant arthrosis and an Outerbridge classification greater than II. Failure is established by previous studies as allograft removal. No patient was lost to follow-up. RESULTS: The success rate was 42 of 47 allografts (89.4%) with a mean failure time of 4.4 years as assessed by Kaplan-Meier survival analysis. Statistical power is greater than 0.9, with alpha = 0.05 and N = 47. There was significant mean improvement in preoperative versus postoperative self-reported measures of pain, activity, and functioning, with P = .001, P = .004, and P = .001, respectively, as assessed by a Wilcoxon rank-sum test with P = .05. CONCLUSIONS: Meniscus allografts can survive in a joint with arthrosis, challenging the contraindications of age and arthrosis severity. These results compare favorably with those in previous reports of meniscus allograft survival in patients without arthrosis. LEVEL OF EVIDENCE: Level IV.

Activities of Daily Living↗