Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Probability Theory”

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 1,117 records · Page 62Linked to original sources
PubMed1996

Expectancy-value approach to drinking non-sugared mineral water among adolescents.

This study set out to predict the intention to drink non-sugared mineral water and the performance of this behavior in a group of Norwegian adolescents using the theories of reasoned action and planned behavior. The empirical data stem from The Norwegian Longitudinal Health Behavior Study, and a comprehensive questionnaire survey was performed in September and October 1992. The study group comprised 970, 15-yr-old adolescents, considered to be representative of this age group in the county of Hordaland. After a 4-week period actual behavior was assessed in a subgroup (n=170). The theories posit that a person will probably perform a behavior if she/he intends to perform the behavior and has actual control with its performance. Behavioral intention is in turn governed by three types of predictors: attitudes, subjective norms and perceived behavioral control. Multiple regression analysis showed that the intention to drink non-sugared mineral water was primarily governed by perceived behavioral control and attitudes while subjective norms had less impact. Intention alone turned out to be the immediate determinant of drinking of non-sugared mineral water, which implies that performance of this behavior presents few problems regarding actual control.

Adolescent↗
PubMed2004

Dewetting of polymeric films: unresolved issues.

Since the early seminal theoretical work by Brochard and coworkers, and experiments by Reiter over a decade ago, considerable progress has been made toward the development of a comprehensive picture of the "equilibrium" and dynamic behavior of unstable thin polymeric films. Generally, theoretical work has carefully guided the design of many experiments conducted in this field. Recent experimental findings, however, raise new questions that could probably not have been foreseen by theory and now need to be revisited. In this paper we highlight three problems in two general areas, (1) the use of the effective interfacial potential describing film substrate interactions and (2) the dynamics of dewetting and the associated connection to "slip" phenomena and fingering instabilities. We suggest that in addition to experiments, analytical theory and simulations will play a critical role toward elucidating the ultimate goal of a universal picture of "equilibrium" and dynamic behavior of instabilities in thin films.

Journal Article↗
PubMedDate not supplied

Withholding information from cancer patients as a physician's decision under risk.

When cancer is diagnosed, the physician may face a dilemma regarding disclosure of information to the patient. While he or she may feel a responsibility to maintain the patient's hope, even through the withholding of information, there is a risk involved: if treatment fails, the patient will eventually know the truth. Patients who would rather live their final days in peace rather than undergo unpleasant treatment of an uncertain nature may be furious and frustrated that they have been deprived of this liberty, ending their lives feeling worse than they would have had they been told the truth at the outset. The author applies three theories of decision making under uncertainty (expected utility theory, prospect theory, and regret theory) to the physician's problem of whether and to what extent to withhold information from a cancer patient, deriving comparative predictions with regard to the relationships between the physician's behavior and illness, patient, and physician characteristics. The results help explain why physicians whose norm of behavior is full disclosure sometimes opt to withhold information and why junior physicians are more likely to disclose the truth than their senior colleagues, as well as the empirical findings that physicians tend to disclose more truthful information to patients the greater the severity of illness and the more inquisitive the patient.

Decision Theory↗
PubMed2006

Score-based prediction of genomic islands in prokaryotic genomes using hidden Markov models.

BACKGROUND: Horizontal gene transfer (HGT) is considered a strong evolutionary force shaping the content of microbial genomes in a substantial manner. It is the difference in speed enabling the rapid adaptation to changing environmental demands that distinguishes HGT from gene genesis, duplications or mutations. For a precise characterization, algorithms are needed that identify transfer events with high reliability. Frequently, the transferred pieces of DNA have a considerable length, comprise several genes and are called genomic islands (GIs) or more specifically pathogenicity or symbiotic islands. RESULTS: We have implemented the program SIGI-HMM that predicts GIs and the putative donor of each individual alien gene. It is based on the analysis of codon usage (CU) of each individual gene of a genome under study. CU of each gene is compared against a carefully selected set of CU tables representing microbial donors or highly expressed genes. Multiple tests are used to identify putatively alien genes, to predict putative donors and to mask putatively highly expressed genes. Thus, we determine the states and emission probabilities of an inhomogeneous hidden Markov model working on gene level. For the transition probabilities, we draw upon classical test theory with the intention of integrating a sensitivity controller in a consistent manner. SIGI-HMM was written in JAVA and is publicly available. It accepts as input any file created according to the EMBL-format.It generates output in the common GFF format readable for genome browsers. Benchmark tests showed that the output of SIGI-HMM is in agreement with known findings. Its predictions were both consistent with annotated GIs and with predictions generated by different methods. CONCLUSION: SIGI-HMM is a sensitive tool for the identification of GIs in microbial genomes. It allows to interactively analyze genomes in detail and to generate or to test hypotheses about the origin of acquired genes.

Algorithms↗
PubMed1977

Clinical information from medical images. A comparison of two types of ultrasonic image in the detection of focal intrahepatic lesions.

If the uncertainty in the diagnosis is measured before and after viewing a diagnostic image, the change in uncertainty is a measure of the information contributed by that image. The formal basis of information theory has been used to calculate the change in uncertainty. These analytical methods have been applied to assess two types of ultrasonic grey-scale image in the demonstration of possible focal intrahepatic lesions.

Humans↗
PubMed1974

Contingency spaces and measures in classical and instrumental conditioning.

The contingency between conditional and unconditional stimuli in classical conditioning paradigms, and between responses and consequences in instrumental conditioning paradigms, is analyzed. The results are represented in two- and three-dimensional spaces in which points correspond to procedures, or procedures and outcomes. Traditional statistical and psychological measures of association are applied to data in classical conditioning. Root mean square contingency, Ø, is proposed as a measure of contingency characterizing classical conditioning effects at asymptote. In instrumental training procedures, traditional measures of association are inappropriate, since one degree of freedom-response probability-is yielded to the subject. Further analysis of instrumental contingencies yields a surprising result. The well established "Matching Law" in free-operant concurrent schedules subsumes the "Probability Matching" finding of mathematical learning theory, and both are equivalent to zero contingency between responses and consequences.

Avoidance Learning↗
PubMed2004

A pilot study on the use of decision theory and value of information analysis as part of the NHS Health Technology Assessment programme.

OBJECTIVES: To demonstrate the benefits of using appropriate decision-analytic methods and value of information analysis (DA-VOI). Also to establish the feasibility and implications of applying these methods to inform the prioritisation process of the NHS Health Technology Assessment (HTA) programme, and possibly extending their use therein. DATA SOURCES: Three research topics that were considered by the HTA panels in the September 2002 and February 2003 prioritisation rounds. REVIEW METHODS: A brief and non-technical overview of DA-VOI methods was circulated to the panels and Prioritisation Strategy Group (PSG). For each case study the results were presented to the panels and the PSG in the form of brief case-study reports. Feedback on the DA-VOI analysis and its presentation was obtained in the form of completed questionnaires from panel members, and reports from panel senior lecturers and PSG members. RESULTS: Although none of the research topics identified met all of the original selection criteria for inclusion as case studies in the pilot, it was possible to construct appropriate decision-analytic models and conduct probabilistic analysis for each topic. In each case, the tasks were completed within the time-frame required by the existing HTA research prioritisation process. The brief case-study reports provided a description of the decision problem, a summary of the current evidence base and a characterisation of decision uncertainty in the form of cost-effectiveness acceptability curves. Estimates of value of information for the decision problem were presented for relevant patient groups and clinical settings, as well as the value of information associated with particular model inputs. The implications for the value of research in each of the areas were presented in general terms. Details were also provided on what the analysis suggested regarding the design of any future research in terms of features such as the relevant patient groups and comparators, and whether experimental design was likely to be required. CONCLUSIONS: The pilot study showed that, even with very short timelines, it is possible to undertake DA-VOI that can feed into the priority-setting process that has been developed for the HTA programme. There are however a number of areas that need to be established at the beginning of the process, such as clarification of the nature of the decision problem for which additional research is being considered, explicitness about which existing data should be used and how data that exhibit particular weaknesses should be down-weighted in the analysis. Other areas, including optimum application of researcher time, integrating the vignette (a summary of the clinical problem and existing evidence) and the use of DA-VOI, training, use of sensitivity analyses, and deployment of clinical expertise, are also considered in terms of the potential implementation of DA-VOI within the HTA programme. Recommendations for further research include how literature searching should focus on those variables to which the model's results are most sensitive and with the highest expected value of perfect information; methods of evidence synthesis (multiple parameter synthesis) to consider the evidence surrounding multiple comparators and networks of evidence; and ways in which the value of sample information can be used by the NHS HTA programme and other research funders to decide on the most efficient design of new evaluative research. There is also a need for an analytical framework to be developed that can jointly address the question of whether additional resources would better be devoted to additional research or interventions to change clinical practice.

Biomedical Technology↗
PubMed1986

Cost-effectiveness of culturing for Chlamydia trachomatis. A study in a clinic for sexually transmitted diseases.

We have evaluated the cost-effectiveness of using cell culture to test for chlamydial infections in 9979 patients at a clinic for sexually transmitted diseases. From results of cultures, we have established prevalence data and, using decision-theory analysis, have calculated costs and probabilities of various outcomes. According to their histories and presenting signs and symptoms, patients were classified as at high or low risk for chlamydial infections. Empiric treatment of all patients attending the clinic was the most cost-effective strategy, followed by empiric treatment of high-risk women and culture-based treatment of low-risk women. Obtaining cultures for men at high and low risk was not cost-effective. If universal treatment is not provided, the most cost-effective strategy appears to be empiric therapy in patients at high risk for chlamydial infections and therapy based on diagnostic test results in women at low risk.

Adolescent↗
PubMedDate not supplied

[Dupuytren's disease and cervical arthrosis].

The Authors, after having briefly discribed Dupuytren's disease in its anatomical and pathological manifestations next discribe the various theories as to causes of the disease. In conclusion they are of the opinion that the theory of arthritis is the most probable, statistically speaking.

Arthritis↗
PubMed2001

["Doghearted" women: the origins of the counting method].

The so called counting-method of contraception was widely used even by the Greeks, though its scientific explanation has been elaborated only in the 1930s by Knaus and Ogino. The Greeks however misunderstood the process of conception and did not follow the periods of humans, but those of other mammals, so their method probably proved to be inefficient. The theory nevertheless, in spite of all experiences, survived for centuries and was still in use even in the 16th century. Author attempts to give an answer to this fact: according to her opinion, based on medical, historical, and literary sources, the mystery could be explained by the Greek concept of genders, and the identification of dogs with women.

Animals↗
PubMedDate not supplied

Understanding the impact of variation in the delivery of healthcare services.

In the past several years, healthcare providers have coped with the financial aspects of managed care and the resultant constraints on revenue. In fact, working with decreasing margins of return has become routine for many providers. Beyond straightforward cost cutting, providers must also consider a variety of other operational factors to achieve success. To this end, higher patient satisfaction and improved utilization and efficiency of resources are natural objectives. Ironically, fundamental to the pursuit of better operations management is the fact that the delivery of healthcare services can vary between and among patients, providers, and organizations for many reasons. Unfortunately, such variation may be overlooked or trivialized if the phenomenon is not well understood by healthcare managers. Knowing how variation affects the delivery of services creates opportunities for focused improvement.

Appointments and Schedules↗
PubMed2005

Genetic and physiological factors in obesity.

Body weight is determined by the interaction of the genetic makeup of an individual and the environment in which that person is living. The control systems that regulate body weight are numerous and include signals from fat that travel to the hypothalamus where cognitive and internal signals are integrated. The integration of these signals involves a complex array of neuropeptides, neurotransmitters and structural circuits. These circuits regulate appetite, intake and energy expenditure. Recent studies demonstrate that the theory of a thrifty genotype is probably correct. Some people are more susceptible to our obesogenic environment than others. Some people are able to overwhelm their genetics by voluntarily increasing energy expenditure and decreasing food intake; a feat that is rarely accomplished and requires a Herculean effort. As we better understand the environmental, genetic, physiological, and behavioral aspects of obesity, we will undoubtedly develop better strategies and therapies for obesity.

Body Mass Index↗