Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Statistics as Topic”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,459 records · Page 81Linked to original sources
PubMed1996

Demographic data collection in less developed countries 1946-1996.

This evolution over the last 50 years of data collection systems in less developed countries is assessed. The progress made by civil registration systems has been extremely disappointing. Except in Central and South America, their role in providing vital rate estimates is still very limited. In contrast, the promulgation of regular population censuses has been a success, particularly in Africa. The relative merits and demerits of different types of demographic surveys are described. To some extent multi-round designs have given way to single-round surveys, such as the Demographic and Health Surveys (DHS). DHS-style enquiries are particularly suitable for evaluation of interventions but are less appropriate if the main aim is to measure vital rates.

Biometry↗
PubMed2003

Implementation of a clinical dementia guideline. A controlled study on the effect of a multifaceted strategy.

OBJECTIVE: To assess the impact of a multifaceted implementation strategy aiming to improve GP adherence to a clinical guideline on dementia. DESIGN: Controlled before and after study using data records from regional laboratories. The guideline was mailed to all GPs. The multifaceted implementation strategy was planned with local GPs, and consisted of seminars, outreach visits, reminders and continuing medical education (CME) small group training. SETTING: Primary health care. SUBJECTS: 535 GP practices with 727 physicians in Denmark. MAIN OUTCOME MEASURES: The diffusion and use of the guideline was measured by a mailed survey. Adherence to guideline recommendations was monitored by data on laboratory tests from general practice in patient's > or = 65 years: thyroid stimulating hormone requested with vitamin B12 or methylmalonate. The use of these tests as part of a diagnostic evaluation of dementia was subsequently verified by a questionnaire to the practices. RESULTS: Of the GPs who read the guideline, 88% found it applicable in primary care. No increase in the adherence to guideline recommendations was observed regarding the use of laboratory tests or cognitive tests in the diagnostic evaluation of dementia in general practice. CONCLUSION: Although GPs regarded the guideline applicable in primary care, no change in practice adherence to guideline recommendations was detected after a multifaceted implementation.

Chi-Square Distribution↗
PubMed1980

Observations on nutritional marasmus in a newly rich nation.

A study was performed in a pediatric hospital in Tripoli, Libya where the familial backgrounds of 50 marasmic infants were compared with those of a group of 50 essentially healthy infants of similar age. Families with marasmic infants had more children but lived in smaller homes than the comparison families. Total income was similar in both sets of families and major consumer items such as television sets, cars, and refrigerators were widely present in both groups. Families with marasmic infants, however, had less literate mothers who tended to breastfeed for shorter periods and to feed purchased pureed baby foods more frequently. The causation of marasmus in these circumstances is probably unhygienic infant feeding despite the availability of clean water and modern kitchen facilities. All 3 factors, adequate housing, adequate income, and an adequately educated mother appear to be necessary simultaneously before infantile marasmus can be prevented.

Africa↗
PubMed1992

Optimal estimate of population age structure with varying vital rates.

The author presents a method for estimating the age distribution of a population under varying vital statistics. "Some mathematical aspects of the method, as well as its applicability, will be discussed and numerical simulation will be run to illustrate the results and to compare the method with the traditional estimate of stable population theory...."

Age Distribution↗
PubMed2002

The Falls-Efficacy Scale, Swedish version: does it reflect clinically meaningful changes after stroke?

PURPOSE: The overall aim of this prospective investigation was to evaluate the ability of the Falls Efficacy Scale (Swedish version) (FES(S)) to reflect clinically meaningful changes over time. METHOD: Changes on the FES(S) scale were compared with changes in two different standardized measures of observer-assessed balance, the Berg Balance Scale (BBS), the Fugl-Meyer balance subscale (FMB), and of motor function and ambulation in 62 stroke patients. Assessments took place on admission for rehabilitation, at discharge and 10 months after the stroke. Indices of effect size were used to evaluate responsiveness of the instruments. Three time periods were studied: admission to discharge (early response), discharge to 10 month follow-up (late response) and admission to follow-up (overall response). RESULTS: The main findings are that the FES(S) is as responsive as BBS and FMB in detecting changes during the early and overall response periods. Changes in FES(S) scores between admission and discharge correlated significantly with changes in observer-assessed balance, motor function and ambulation scores. CONCLUSIONS: The present results suggest that measurement of perceived confidence in task performance using the FES(S) scale is responsive to improvement in patients with hemiparesis at an early stage after stroke.

Accidental Falls↗
PubMed1997

Application of rank analysis of covariance methods to analysis of multiple anatomical regions with treatment for seborrheic dermatitis.

This paper presents the advantages of rank analysis of covariance in contrast to the Mantel-Haenszel procedure in the presence of a covariate. In this paper, data from a clinical trial with an indication for seborrheic dermatitis, which afflicts multiple anatomical regions, is presented. This paper presents analysis performed using both the Mantel-Haenszel procedure and rank analysis of covariance for separate anatomical regions, as well as for the combined anatomical regions. The analysis for the combined anatomical regions involves weighted sums over different strata.

Dermatitis, Seborrheic↗
PubMed1997

Interim analyses and early termination of clinical trials.

The group sequential tests (GST) are appropriate for performing interim analyses in clinical trials. Various GST are reviewed and compared in this paper in terms of the expected sample size, the maximum sample size, and other practical aspects. Also discussed are the p-values of the significant differences for GST. Common problems and difficulties of using GST in practice are examined. One problem is difficulties associated with the delayed data accumulated after a trial is terminated at an interim test. The GST with O'Brien-Fleming type of boundaries are found to be safe in dealing with delayed observations. Possible approaches for performing futility analyses are illustrated with examples. It is recommended that futility analysis with GST be built into the design of large clinical trials.

Clinical Trials as Topic↗
PubMed1999

Complementary nonparametric analysis of covariance for logistic regression in a randomized clinical trial setting.

In the randomized clinical trial setting, controlling for covariates is expected to produce variance reduction for the treatment parameter estimate and to adjust for random imbalances of covariates between the treatment groups. However, for the logistic regression model, variance reduction is not obviously obtained. This can lead to concerns about the assumptions of the logistic model. We introduce a complementary nonparametric method for covariate adjustment. It provides results that are usually compatible with expectations for analysis of covariance. The only assumptions required are based on randomization and sampling arguments. The resulting treatment parameter is a (unconditional) population average log-odds ratio that has been adjusted for random imbalance of covariates. Data from a randomized clinical trial are used to compare results from the traditional maximum likelihood logistic method with those from the nonparametric logistic method. We examine treatment parameter estimates, corresponding standard errors, and significance levels in models with and without covariate adjustment. In addition, we discuss differences between unconditional population average treatment parameters and conditional subpopulation average treatment parameters. Additional features of the nonparametric method, including stratified (multicenter) and multivariate (multivisit) analyses, are illustrated. Extensions of this methodology to the proportional odds model are also made.

Humans↗
PubMed1999

Nonparametric analysis of covariance for hypothesis testing with logrank and Wilcoxon scores and survival-rate estimation in a randomized clinical trial.

Many clinical trials have time-to-event variables as principal response criteria. When adjustment for covariates is of some importance, the relative role of methods for such analysis may be of some concern. For the Wilcoxon and logrank tests, there is an issue of how covariance adjustment can be nonparametric in the sense of not involving any further assumptions beyond those of the logrank and Wilcoxon test. Also of particular interest in a clinical trial is the estimation of the difference between survival probabilities for the treatment groups at several points in time. As with the Wilcoxon and logrank tests, there is no well known nonparametric way to incorporate covariate adjustment into such estimation of treatment effects for survival rates. We propose a method that enables covariate adjustment for hypothesis testing with logrank or Wilcoxon scores. Related extensions for applying covariate adjustment to estimation of treatment effects are provided for differences in survival-rate counterparts to Kaplan-Meier survival rates. The results represent differences in population average survival rates with adjustment for random imbalance of covariates between treatment groups. The methods are illustrated with a clinical trial example.

Humans↗
PubMed2005

A nonparametric comparison of the effectiveness of treatments: a multivariate toxicity-penalized approach.

In cancer clinical trials, the amount of treatment dose actually received by a patient may be limited by severe toxicity or lack of efficacy. A nonparametric approach is proposed for comparing the effectiveness of treatments based on the bivariate relationship defined by the doses at which efficacy and toxicity are observed to occur. Simulation studies are used to contrast the performance of the new procedure with the usual method of comparing percentages of patients who have effective results. Data from a randomized clinical trial of patients with metastatic nonseminomatous germ cell tumors are used to illustrate the method.

Antineoplastic Agents↗
PubMed2003

Citation indexes do not reflect methodological quality in lung cancer randomised trials.

BACKGROUND: Citation factors are applied to assess scientific work despite the fact that they were developed commercially in order to compare competing journals. The aim of the present study was to determine whether there is a relationship between citation factors and a trial's methodological quality using published randomised trials in lung cancer clinical research. Material and methods All of the randomised trials included in nine systematic reviews performed by the European Lung Cancer Working Party (ELCWP) were assessed using two quality scales (Chalmers and ELCWP). RESULTS: One hundred and eighty-one articles were eligible. The median overall ELCWP and Chalmers quality scores were 61.8% and 49.0%, respectively, with a correlation coefficient (r(s)) of 0.74 (P <0.001). A weak association was observed between citation factors and quality scores with the respective correlation coefficients ranging from 0.18 to 0.40 (ELCWP scale) and from 0.21 to 0.38 (Chalmers scale). American authors published trials significantly more often in journals with high citation factors than European or non-American authors (P <0.0001), despite no better methodological quality. Positive trials, which were significantly more likely to be published in journals with higher citation factors, were of no better quality than negative ones. CONCLUSION: Journals with higher citation factors do not appear to publish clinical trials with higher levels of methodological quality, at least for trials in the field of lung cancer research.

Chi-Square Distribution↗