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PubMed1999

The controversy of significance testing: misconceptions and alternatives.

The current debate about the merits of null hypothesis significance testing, even though provocative, is not particularly novel. The significance testing approach has had defenders and opponents for decades, especially within the social sciences, where reliance on the use of significance testing has historically been heavy. The primary concerns have been (1) the misuse of significance testing, (2) the misinterpretation of P values, and (3) the lack of accompanying statistics, such as effect sizes and confidence intervals, that would provide a broader picture into the researcher's data analysis and interpretation. This article presents the current thinking, both in favor and against, on significance testing, the virtually unanimous support for reporting effect sizes alongside P values, and the overall implications for practice and application.

Bias↗

PubMed2002

[Survival after myocardial infarction among the middle-aged Kaunas men and women].

UNLABELLED: The aim of the present study was to determine and compare the short-term and long-term survival after myocardial infarction (MI) in the Kaunas men and women aged 25-64 during 1983 to 1998, according to ischemic heart disease register data. The source of the data--Kaunas population-based ischemic heart disease register. The diagnosis of MI was based on the criteria defined by the WHO MONICA Project. All myocardial infarction events that occurred among Kaunas population aged 25-64 years during 1983-1998 were recorded. Myocardial infarction survival was evaluated using Kaplan-Meier method and using z test for comparing the survival curves. RESULTS: The data of 3,613 persons with a first myocardial infarction and 528 with a recurrent myocardial infarction were analyzed. Detected, that among men and women a short-term (28 days) survival probability was significant different. In the men aged 25-64 short-term survival after a first myocardial infarction was better comparing with the women survival (z = 4.63, p = 0.03). The short-term survival among men aged 25-64 with a recurrent myocardial infarction comparing with woman did not differ. The long-term survival probability in patients, who survived the first 28 days, among men and women with a first and recurrent myocardial infarction aged 25-64 was without statistically significant differences.

Adult↗

PubMed1989

A system for on-line detection and resolution of radiolabeled DNA molecules and its application to automated DNA sequence analysis.

We describe a system for the real-time detection of radioactively labeled DNA molecules in gel matrix, and we demonstrate the application of this system to DNA sequence analysis. DNA sequencing reactions prepared by the Sanger chain termination method are resolved by electrophoresis on 8% polyacrylamide gels. During electrophoresis the 32P-labeled DNA fragments are detected by solid state detectors positioned 22 cm from the top surface of the gel. This system is able to resolve a DNA sequence of 300 bases or greater. Optimized protocols that allow sequence information to be obtained from single stranded and double-stranded templates are described. A linear relationship exists between the input dpm and the integrated peak values over a 20-fold range indicating that accurate DNA quantitation is also possible using this system.

Automation↗

PubMed1998

A review of selection criteria used by medical scheme advisers to approve or deny procedures with a cosmetic component.

OBJECTIVE: To review and apply statistical tests to the selection criteria used by two medical advisers to approve or deny applications for three common cosmetic or reconstructive procedures within a large group of medical schemes. DESIGN: A retrospective descriptive study which applied multiple regression analysis, frequency analysis, comparison of means and simple correlations to the data sets for three procedures. SETTING: Administrative records from the clinical files of medical advisers and the administrator's claims database. SUBJECTS: Data were reviewed for 1,143 members who, between January and December 1996, submitted applications for breast reduction, excimer laser refractive surgery, or otoplasty. MAIN OUTCOME MEASURES: The primary outcome measure was the statistical relationship between medical advisers' selection criteria and final decision. In addition, the financial implications of these cosmetic/reconstructive procedures were assessed. RESULTS: For the three procedures reviewed there was a statistically significant relationship between 5 of 13 preoperative criteria requested and the medical advisers' opinion. Excimer laser surgery was generally approved on the basis of the refractive error (myopia > -3.00; astigmatism > -1.5 dioptres); otoplasty was generally approved for children aged > or = 12 years; and breast reduction was usually covered for women with a sternal-nipple distance > 29.0 cm and with a cup size > or = DD. The other data submitted were similarly distributed between the approved and denied groups. CONCLUSIONS: Review of medical advisers' decisions is important in an era of protocols, guidelines and 'standard operating procedures'. Selection criteria for approval of applications for medically necessary cosmetic/reconstructive surgery must be reviewed and revised to provide a reliable, reproducible and statistically valid process.

Child↗

PubMed2002

Some aspects regarding the interpretation of influenza surveillance data.

For influenza monitoring, the use of laboratory data usually in combination with morbidity data from primary care facilities is common. The estimated excess morbidity, or resulting rates and consultation incidences are the basic parameter for the estimation of influenza activity in conjunction with antigen assays of influenza in a selected sub-sample of the recorded patients. The interpretation of such data is complicated by several selection processes, confounding influences and bias. The case definition (CD) given for the selection of cases is important for the sensitivity and specificity of the registrations. For the clinical morbidity data, the lower specificity found when more general (acute respiratory tract infections) criteria are used seems to be compensated by a higher statistical sensitivity due to the larger number of cases. The relative stability of the background morbidity against the expected values is critical for the interpretation. The sub-sample of patients tested by antigen assays is usually small due to cost constraints. Testing all patients with the defined symptoms in a sub-sample of practices is rarely possible because of the workload in the GPs offices during an influenza epidemic but does allow the number of positives to be used as an indicator. Usually, a sub-sample of GPs is asked to test a limited number of patients suffering with the symptoms given as selection criteria. In this case, the rate of positives is the better indicator for the influenza activity. However, the low number of tests particularly when flu is circulating at a low level limits the statistical sensitivity of this parameter. The specificity of the criteria given for the selection of patients being swabbed and the sensitivity of the test largely determine the function between the rate of positives and the influenza activity. The virological results are mostly interpreted in a more qualitative way, to see if influenza is circulating significantly. For this interpretation, more specific selection criteria (CD) seem useful and a high sensitivity for an increasing circulation can be expected.

Data Interpretation, Statistical↗

PubMed1990

Combining statistical, rule-based, and physiologic model-based methods to assist in the management of diabetes mellitus.

Self-monitoring of capillary blood glucose is used by most patients with insulin-dependent diabetes mellitus as a means of assessing metabolic control. Therapeutic interventions are based on retrospective analysis of glycemic response to various factors, with insulin and diet playing the key roles. We describe a computer system being developed for intelligent automated analysis and interpretation of data relevant to glycemic control. CADMO (Computer-Assisted Diabetes Monitor) is intended to assist health care professionals with the management of patients with insulin-dependent diabetes. It takes as input glucose values and insulin doses collected via a memory meter by the patient over a period of several weeks. Rule-based logic, statistical methods, and a physiologic model of insulin pharmacokinetics and glucose dynamics are used to help detect meaningful patterns and trends in glucose and insulin data and to suggest approaches for optimizing insulin regimens.

Blood Glucose↗

PubMed1992

[Interpretation of experimental data in the presence of accidental perturbations: characterization of the bladder].

Some tests are subject to the influence of a special kind of "irreducible" effects which do not satisfy the Central Limit Theorem of statistics, even though they show no systematic character or tendency. These effects especially present when physiological experiments are concerned "in vivo". In such the lack of specific methods to reduce these effects brings about the necessity of special case in minimizing the loss of information. Contained in the experimental data as well as the accumulation of useless information. Recent work has suggested the extensive use of several indexes derived from combination of available variables and their respective mathematic correlation. The information obtained by following this methodology has the character of "working hypothesis" so it needs many favorable confirmation to assess its reliability. It is convenient to analyze a large number of relations in order to emphasize the concordant effects and discord the others. In order to obtain some preliminary indication of the reliability of this procedure we have analyzed some CMG curves in prostatic and non-prostatic subject. The final slope of the curves (urge point) t = dP/dVr has been adapted as an index of the "elasticity" of the bladder; it was compared with the filling volume, the muscular volume and their ratio, i.e. with a geometric index of the bladder shape. The correlation show that the index t can, to some extent significantly represent the mechanical behaviour of the bladder in its physiological condition or when there is a partial obstruction of urine deflection.(ABSTRACT TRUNCATED AT 250 WORDS)

Artifacts↗

PubMedDate not supplied