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PubMed2004

[Guidelines for writing biomedical articles containing statistical figures and analysis].

Some advices are provided in order to make statistical figures and analyses more correct in biomedical articles. The sample size has an outstanding significance. Analysing different statistical relationships the requirements of biometry should be fulfilled (number and distribution of data etc.) and interpretation of statistical findings could be done only within the domain of minimal and maximal values of independent variable. Extrapolation is not recommended due to the specific nature of the biomedical system. In some cases laboratory data should be transformed mathematically and the results of subsequent statistical calculations should be retransformed back into the biomedical system.

Biometry↗

PubMed2004

[Statistic-mapping modeling of rheumatic diseases prevalence among population of different regions of Russia].

AIM: To assess feasibility of the method of mapping modeling for spacial featuring of rheumatic diseases (RD) morbidity statistics for population of Russia. MATERIAL AND METHODS: Population morbidity statistics for 78 administrative units of the Russian Federation (1993-2000) were processed. Statistic-mapping modeling employed weighted mean interpolation i.e. mathematic prediction of the sign value depending on its magnitude in basic points. RESULTS: Mapped images of RD prevalence, prevalence/primary morbidity values and number of documented cases/number of rheumatologists demonstrate special distribution of the signs studied about the RF territory. The estimation of mean, minimal, maximal values and dispersion of each sign established dynamic trends in the markers for the period under study(increased area with RD prevalence above 95/1000 from 15.9 to 44.5%; increased mean ratio prevalence/morbidity from 2.8 to 3.2 and decreased ratio of patients/rheumatologists from 10882 to 9031). Regions with minimal and maximal values are shown. CONCLUSION: Statistic-mapping modeling demonstrates spacial distribution of the markers, reveals the relations between them.

Humans↗

PubMed1992

Statistical conclusion validity and type IV errors in rehabilitation research.

The incidence of type IV errors was examined in 71 rehabilitation research studies, including a two-way analysis of variance with a statistically significant interaction. The interpretation of the significant interaction was examined to determine whether it qualified as a type IV error. A type IV error was defined as the incorrect interpretation of a correctly rejected null hypothesis. Statistically significant interactions were classified in one of the following categories: (1) correct interpretation, (2) cell mean interpretation, (3) main effect interpretation, or (4) no interpretation. Interpretations classified as cell means or main effects were considered type IV errors. The analysis revealed that 21% of the interactions were correctly interpreted and 63% of the interactions were classified as type IV errors. The remaining 16% of the studies showed a statistically significant interaction but no interpretation. The implications of statistical conclusion validity and type IV errors are discussed, and methods to eliminate or reduce the incidence of type IV errors in rehabilitation research are presented.

Analysis of Variance↗

PubMed2004

Scan statistics for temporal surveillance for biologic terrorism.

INTRODUCTION: Intentional releases of biologic agents are often designed to maximize casualties before diagnostic detection. To provide earlier warning, syndromic surveillance requires statistical methods that are sensitive to an abrupt increase in syndromes or symptoms associated with such an attack. OBJECTIVES: This study compared two different statistical methods for detecting a relatively abrupt increase in incidence. The methods were based on the number of observations in a moving time window. METHODS: One class of surveillance techniques generates a signal based on values of the generalized likelihood ratio test (GLRT). This surveillance method is relatively well-known and requires simulation, but it is flexible and, by construction, has the appropriate type I error. An alternative surveillance method generates a signal based on the p-values for the conventional scan statistic. This test does not require simulation, complicated formulas, or use of specialized software, but it is based on approximations and thus can overstate or understate the probability of interest. RESULTS: This study compared statistical methods by using brucellosis data collected by CDC. The methods provided qualitatively similar results. CONCLUSIONS: Relatively simple modification of existing software should be considered so that when GLRTs are performed, the appropriate function will be maximized. When a health department has data that indicate an unexpected increase in rates but its staff lack experience with existing software for surveillance based on GLRTs, alternative methods that only require computing Poisson probabilities can be used.

Bioterrorism↗

PubMed2006

[Prognosis of remote consequences of combat mental trauma using logical statistical methods].

Prognosis of remote consequences of acute stress disorders and adaptation disorders as posttraumatic stress disorders (PTSD) is possible using relevant mathematical methods. The authors have used the following logical statistical methods: algorithms for search and statistical verification of optimal fragmentation of variables in multi-dimensional space ("Q-nearest neighbors", "statistically weighed syndromes") as well as a program of searching for multiple conjunctions of variables that allowed to single out statistically significant combinations of variables (p<0,001) and to divide the sample into two groups: with favorable and with unfavorable outcome both at the acute and remote stages of mental trauma. Predictors of unfavorable outcome found in the acute period of mental trauma were as follows: affective tension, impulsivity, high personal anxiety and depressive tendencies with reduced activity. Comparing to clinical evaluation, subjective criteria of mental state (self-rating) retained its informativeness for prognosis of protracted PTSD types. Using this set of variables, it became possible to predictt remote consequences (2-4 years) of psychogenias of combat situation with reliability of recognition of 85% for the favorable outcome and 79% for cases of protracted types.

Adolescent↗

PubMed2006

Strabismus outcomes/quality control: the application of statistical process control (SPC) to one muscle and two muscle simple horizontal strabismus of 25 PD or less.

INTRODUCTION: Statistical Process Control (SPC) techniques were originally used for evaluating quality in manufacturing. The SPC chart consists of data plotted in a time sequence with the mean and upper and lower control limits (approximates +/- 3 standard deviations), graphically showing trends in the data. We employed SPC charts to analyze one and two muscle surgery for simple horizontal strabismus of 25 prism diopters (PD) or less. METHODS: We reviewed the records of 47 patients, 18 years and younger with consistent preoperative strabismus measurements of 25 PD or less, who underwent pure horizontal rectus muscle recession, resection, or both. SPC charts were used to compare the differences in preoperative and postoperative measurements of one muscle versus two muscle esotropia and exotropia using the QI analyst software package. RESULTS: The average preoperative measurements for esotropia were 19.6 PD of one muscle cases, and 23.8 PD for two muscle cases. For exotropia, these values were 16.7 PD for one muscle cases and 20.6 PD for two muscle cases. The average postoperative measurements for esotropia were 5.4 PD for one muscle cases, and 10.0 PD for two muscles cases. For exotropia, the values were 2.2 PD for one muscle cases, and 11.0 PD for two muscle cases. SPC charts displaying pre- and postoperative measurements for one and two muscle surgery for both esotropia and exotropia showed normal statistical fluctuation. Interestingly, two muscle postoperative measurements for both esotropia and exotropia had higher upper control limits (UCL) than one muscle measurements. Those patients requiring additional surgery, or whose postoperative measurements were greater than 15 PD were considered failed cases. The differences in failure rates between one muscle and two muscle cases were not "statistically significant" [p less than 0.05]. CONCLUSION: One muscle horizontal rectus surgery should be considered as an option when planning surgical treatment for medium angle strabismus. Statistical process control may be a valuable method to analyze variability in many ophthalmologic procedures, with the goal of minimizing variability to achieve better outcome.

Adolescent↗

PubMed2006

Selecting the right statistical model for analysis of insect count data by using information theoretic measures.

Researchers and regulatory agencies often make statistical inferences from insect count data using modelling approaches that assume homogeneous variance. Such models do not allow for formal appraisal of variability which in its different forms is the subject of interest in ecology. Therefore, the objectives of this paper were to (i) compare models suitable for handling variance heterogeneity and (ii) select optimal models to ensure valid statistical inferences from insect count data. The log-normal, standard Poisson, Poisson corrected for overdispersion, zero-inflated Poisson, the negative binomial distribution and zero-inflated negative binomial models were compared using six count datasets on foliage-dwelling insects and five families of soil-dwelling insects. Akaike's and Schwarz Bayesian information criteria were used for comparing the various models. Over 50% of the counts were zeros even in locally abundant species such as Ootheca bennigseni Weise, Mesoplatys ochroptera Stål and Diaecoderus spp. The Poisson model after correction for overdispersion and the standard negative binomial distribution model provided better description of the probability distribution of seven out of the 11 insects than the log-normal, standard Poisson, zero-inflated Poisson or zero-inflated negative binomial models. It is concluded that excess zeros and variance heterogeneity are common data phenomena in insect counts. If not properly modelled, these properties can invalidate the normal distribution assumptions resulting in biased estimation of ecological effects and jeopardizing the integrity of the scientific inferences. Therefore, it is recommended that statistical models appropriate for handling these data properties be selected using objective criteria to ensure efficient statistical inference.

Animals↗

PubMedDate not supplied

Statistical process control for the pharmaceutical industry.

An overview of Total Quality Management and Statistical Process Control is provided with a goal of focusing on their implementation. The implementation is presented as three distinct areas. These are the philosophical and behavioral requirements, the statistical monitoring, and the statistical design. The first emphasizes the culture of problem solving and continuous improvement, the second focuses on the control charts, and the third on the Taguchi methods. After this overview, a discussion of common mistakes that occur in practice during the implementation of these methods is provided. Again, managerial mistakes are separated from the more specific technical or statistical mistakes. The paper concludes with recommendations concerning applications specific to the pharmaceutical industry.

Inservice Training↗

PubMed1990

A statistical analysis of the third UKEMS collaborative trial.

In the third UKEMS collaborative trial, nine laboratories optimized protocols for a variety of mammalian cell mutagenicity assays and used these protocols to test three reference mutagens. Data from the trial have been deposited with Mutagenesis under the scheme of the journal for a database of results of extensive mutagenicity testing programmes. A preliminary examination of the data using procedures advocated by the UKEMS guidelines on statistical evaluation of mutagenicity test data confirms that the assays are capable of giving clear, convincing data, in a form amenable to statistical analysis. The utility of the methods of analysis proposed by both the plate and fluctuation test statistical working groups was confirmed. In almost all cases variation between plates or trays from the same replicate treatment was little greater than Poisson or binomial, whereas variation between replicate treatments was substantially larger, confirming the recommendation of both groups for true independent replicates of each treatment. In six out of nine laboratories part of this variation between replicates was consistent for both viability and mutation, which might cause the guide-lines procedure for fluctuation test data to underestimate significance. In about half the cases examined, variation between experiments was significantly greater than variation between replicates within an experiment, which may create problems of interpretation. Supplementary tests, using the statistical package GLIM, suggested that although factors such as choice of expression time, level of S9, zero dose cloning efficiency or spontaneous mutation frequency might have an effect, they would not have been likely to interfere with detection of a mutagenic effect in the present data set.

Analysis of Variance↗

PubMed1990

[Use of public health statistics in the development of community diagnosis].

A community diagnosis which describes the health of the local population may be an important instrument in promoting health and preventing disease. Most general practitioners do not have time to carry out individual surveys in the local community. Therefore it seems relevant to look into the possibility of utilizing official health statistics as a basis for community diagnosis. We obtained and analysed demographic data, mortality data, statistics on cancer, data on causes of invalidity and risk factors for cardiovascular diseases for Askvoll municipality. This article demonstrates possibilities, obstacles and constraints in the use of such statistics. Suppliers of register data should make routine health statistics more available for use in the district health services. In this connection we recommend the development of a central health data information system.

Community Health Services↗

PubMed1990

An exploratory study of statistical assessment of papers published in the British Medical Journal.

Statistical assessment of papers submitted to the British Medical Journal has increased to some 300 papers annually. The assessment produces a recommendation to the editor on each paper from a statistical viewpoint together with a completed checklist that indicates the quality of certain important features. This exploratory study was aimed at monitoring the process. It reports a comparison of checklist answers on 45 papers as originally submitted with those on the papers as subsequently published. Of the 45 papers, only 5 (11%) were considered statistically acceptable at submission, but this increased to 38 (84%) after publication. Revisions had not been made adequately in 4 of the 7 unsatisfactory published papers, and the 3 others were thought to be of dubious validity. A major omission from at least 28 papers was information on sample size calculations. It is concluded that statistical assessment is beneficial but that further efforts by authors and assessors could make it even more effective.

Peer Review↗

PubMed1986

Frequency and diversity of use of statistical techniques in oncology journals.

We describe the frequency with which various statistical techniques are reported in almost 5,000 articles published in five major American oncology journals during 1983 and 1984. A reader familiar with about a dozen techniques can expect to understand approximately 90% of the quantitative concepts cited in these journals. With the exception of survival analysis, these were typically the techniques encountered in many introductory statistical texts. Oncology training program preceptors concerned about making their graduates more effective consumers of the literature can use these findings in structuring exposure to quantitative skills. In four of the five journals reviewed, failure to identify the statistical methodology was among the ten most commonly encountered "techniques." This made it impossible to identify the analytical procedures used in many articles, and hence to judge their scientific validity. We encourage more editorial boards to adopt guidelines requiring a standardized format for presenting results based on a statistical analysis.

Actuarial Analysis↗

PubMed1989

The validity of Maori mortality statistics.

Data from an Auckland coronary heart disease register have been used to assess the validity of Maori mortality statistics produced by the National Health Statistics Centre. During the period 1983-4, 804 people aged 35-64 years and resident in the Auckland statistical region, were identified by both the register and death registration data as having died of coronary heart disease. The coronary heart disease register failed to classify the ethnicity of thirteen of these people. Of the remaining 791 cases, the register classified 80 as Maori while only 44 were classified as Maori in the national death registration data; over the period 1983-4 Maori mortality due to coronary heart disease in the Auckland statistical region was understated by 82% (80-44/44). Although some of this discrepancy may be due to differences in classification of ethnicity, the major reason for the understatement is missing information on the death registration form. Simple changes in the documentation of ethnicity could markedly reduce the degree of underreporting.

Adult↗

PubMed1987

A comparison of statistical outcome variables in extremely low birth weight infants.

Three different summary statistics of developmental outcome are described. These include the "handicap ratio" (handicapped individuals divided by survivors), the "handicap rate" (handicapped individuals divided by live births for that birth weight group), and the "handicaps per 10,000 live births" (handicapped individuals divided by 10,000 live births for a geographic region). An analysis of these statistics was undertaken using a sample of extremely low birth weight (ELBW) (less than 1,001 g) infants born in Hawaii during the period of 1975-1981. The results of this study showed a poor correlation between these summary statistics. The results suggest that these statistics represent different aspects of outcome in the ELBW infant. Suitable uses for each of these variables is discussed.

Birth Rate↗

PubMed1988

Annual summary of vital statistics--1987.

Data for this article, as in previous reports, are drawn principally from Monthly Vital Statistics Report, published in the National Center for Health Statistics (NCHS). The international data come from the annual Demographic Yearbook and the quarterly Population and Vital Statistics Report, both published by the Statistical Office of the United Nations, which has also been kind enough to provide directly more recent data reported by various countries. US data for 1987 are estimates by place of occurrence, based upon a count of all certificates received in state offices between two dates, one month apart, regardless of when the event occurred. Mortality data by cause and age, however, come from the Current Mortality Sample, a systematic 10% of those certificates, and thus may not correspond to the actual month of death. For the US as a whole the estimates, with few exceptions, are close to the subsequent final figures. There are considerable variations in some states, however, particularly in comparing provisional figures by place of occurrence and final data by place of residence. State information should be interpreted cautiously. Careful attention should be paid to differing denominators when studying rates presented in this article. For overall rates, like the birth rate or death rate, the standard denominator is 1,000 total population. In instances in which more refined analysis is possible, other denominators are used, such as 100,000; the character of the population is specified. The particular denominator is indicated in the table or in the context.

Birth Rate↗

PubMed1988

Esophagovisceral anastomotic leak. A prospective statistical study of predisposing factors.

An esophagovisceral anastomotic leak is a life-threatening postoperative complication, especially in the mediastinum. Of the 242 patients who underwent intrathoracic esophagogastric anastomosis for esophageal carcinoma (182 patients) and adenocarcinoma of the cardia (60 patients) between January 1980 and June 1985, 14 (5.8%) had esophageal anastomotic leakage and two died (0.8%). Various clinical and biologic parameters and aspects of operative technique were studied prospectively and analyzed statistically to identify possible factors responsible for leaks. Both bivariate and multivariate statistical analysis with logistic regression showed that the following clinical and biologic factors do not influence anastomotic leakage: tumor stage, the curative or palliative purpose of resection, neoplastic permeation of anastomotic margins, total protein concentration below 5 gm/dl, albumin concentration below 3 gm/dl, patient's age, diabetes, high blood pressure, cirrhosis of the liver, and cardiac, respiratory, or renal diseases. Technical factors, on the contrary, were statistically significant and of great clinical importance: manual as opposed to mechanical suturing (chi 2 = 8.8, p = 0.013) and single-layer as opposed to double-layer suturing (chi 2 = 9.9, p = 0.043). The level of the anastomosis was found to be a further statistically significant factor: The incidence of leakage was greater when the anastomosis was located between the azygos vein and the lower pulmonary vein (chi 2 = 15.5, p = 0.004) than above the azygos vein or below the lower pulmonary vein.

Adenocarcinoma↗

PubMed1987

Annual summary of vital statistics--1986.

Data from this article, as in previous reports, are drawn principally from Monthly Vital Statistics Report, published by the National Center for Health Statistics (NCHS). The international data come from the Demographic Yearbook and the quarterly Population and Vital Statistics Report, both published by the Statistical Office of the United Nations, which has also been kind enough to provide directly more recent data. Except for mortality data by cause and age, which are based on a 10% sample, all the US data for 1986 are estimates by place of occurrence, based upon a count of certificates received in state offices between two dates, 1 month apart, regardless of when the event occurred. Experience has shown that for the country as a whole the estimates, with few exceptions, are close to the subsequent final figures. There are considerable variations in some states, however, particularly in comparing provisional figures by place of occurrence and final data by place of residence. State information should be interpreted cautiously. Careful attention should be paid to the denominator when studying rates presented in this article. For overall rates, like the birth rate or death rate, the standard denominator is 1,000 total population. In instances where more refined analysis is possible, the denominator may be 100,000 and the character of the population specified. The particular denominator is indicated in the table or in the context.

Birth Rate↗

PubMed1986

Annual summary of vital statistics--1985.

Data for this article, as in previous reports, are drawn principally from Monthly Vital Statistics Report, published by the National Center for Health Statistics (NCHS). The international data come from the Demographic Yearbook and the quarterly Population and Vital Statistics Reports, both published by the Statistical Office of the United Nations, which has also been kind enough to provide directly more recent data. Except for mortality data by cause and age, which are based on a 10% sample, all the US data for 1984 are estimates by place of occurrence, based upon a count of certificates received in state offices between two dates, 1 month apart, regardless of when the event occurred. Experience has shown that for the country as a whole the estimates, with few exceptions, are close to the subsequent final figures. There are, however, considerable variations in some states, particularly in comparing data by place of occurrence and place of residence. State information should be interpreted cautiously.

Birth Rate↗