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Results for “Probability Theory”

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At least 883 records · Page 49Linked to original sources
PubMed2001

Multilevel performance probability: a meta-analytic integration of expectancy and self-efficacy.

A meta-analysis of one approach to measuring expectancy and self-efficacy was conducted. Although used for over 25 years, this measure has yet to be named or integrated across the two theoretical domains. We proposed to label this measure a Multilevel Performance Probability and conducted a meta-analysis. The search for empirical tests of expectancy and self-efficacy using this procedure yielded 16 studies with ratings which could be subjected to meta-analysis. Five studies with 8 tests were taken from expectancy studies and 11 studies with 47 tests from studies of self-efficacy. In total, the analyses involved 7,444 subjects across 55 tests of the Multilevel Performance Probability to performance relationship. Examination of the measure as a predictor of performance gave a mean r of .51 (p<.001) which is in the same direction and larger than values from other meta-analyses conducted within each of the two theoretical domains (rs of .21 and .38).

Humans↗
PubMed2005

What is preexisting strength? Predicting free association probabilities, similarity ratings, and cued recall probabilities.

Measuring lexical knowledge poses a challenge to the study of the influence of preexisting knowledge on the retrieval of new memories. Many tasks focus on word pairs, but words are embedded in associative networks, so how should preexisting pair strength be measured? It has been measured by free association, similarity ratings, and co-occurrence statistics. Researchers interpret free association response probabilities as unbiased estimates of forward cue-to-target strength. In Study 1, analyses of large free association and extralist cued recall databases indicate that this interpretation is incorrect. Competitor and backward strengths bias free association probabilities, and as with other recall tasks, preexisting strength is described by a ratio rule. In Study 2, associative similarity ratings are predicted by forward and backward, but not by competitor, strength. Preexisting strength is not a unitary construct, because its measurement varies with method. Furthermore, free association probabilities predict extralist cued recall better than do ratings and co-occurrence statistics. The measure that most closely matches the criterion task may provide the best estimate of the identity of preexisting strength.

Comprehension↗
PubMedDate not supplied

Cell senescence in human aging: a review of the theory.

Cell senescence limits cell divisions in normal somatic cells and may play a central role in age-related diseases. In this review, we examine the theory that cell senescence underlies and is a pivotal event in human aging and age-related diseases. The model remains completely consistent with what we currently know of cell biology, cell senescence, and the pathology of all human age-related diseases including atherosclerosis, osteoarthritis, immune senescence, skin aging, Alzheimer's dementia, and cancer. Although there is in vitro and ex vivo data to support the model, there is currently no in vivo data supporting the theory. Such data is probably obtainable using available methods and, if confirmatory, would not only have stunning therapeutic consequences, but significant commercial consequences as well.

Aging↗
PubMed1975

The development of children's understanding of proportions.

To determine whether the understanding of proportions develops before formal operations, children in grades 1, 3, and 5 and college students were given a variety of judgment tasks contrasting the comparison of quantity with the comparison of proportions. Results for the most difficult tasks indicated that a majority of fifth graders still lacked a full understanding of proportion. Results were interpreted as consistent with Inhelder and Piaget's contention that the comprehension of abstract relations requires formal operations. In grades 3 and 5, boys scored significantly higher than girls.

Adult↗
PubMedDate not supplied

[Immune events in central nervous system of early and late onset Alzheimer's disease patients].

INTRODUCTION: Alzheimer s disease (AD) is a progressive degenerative disease affecting a significant proportion of the elderly population. The disease is characterized clinically by a progressive loss of memory function and mental impairment associated with the presence of degenerative well known pathological lesions. Although, the pathogenesis of AD is unclear; several reports indicate the involvement of immune factors. PATIENTS AND METHODS: This paper evaluates some cerebrospinal fluid immune markers from 21 patients with early and late AD and 20 age matched non-demented subjects. The analytical method included the evaluation of T cell subpopulations (using AcMc CD2, CD4, CD8) and activated T cells (AcMc HLA-DR and CD25) from CSF and peripheral blood by immunocytochemical techniques on a fixed cell slide as described by Bernd. The lymphocyte phenotype expressed as a percentage of positively stained cells for each cell surface marker evaluated. RESULTS: Some significant differences were observed for T cell subpopulations from different compartments, between the different AD groups and the controls (p< 0.05). Nevertheless, the most significant differences were found in the activated T cells from cerebrospinal fluid between AD groups and controls (p< 0.01). CONCLUSIONS: These results support the theory of neuroimmune dysregulation, probably involved in the progressive neurodegeneration and dementia in some AD.

Age of Onset↗
PubMed2001

From tobacco to health care and beyond--a critique of lawsuits targeting unpopular industries.

The 1998 settlement between state Medicaid agencies and the five major tobacco companies heralded a new form of litigation in which individual or government plaintiffs allied with private class action attorneys use economic, political and moral leverage to extract huge settlements from entire industries. Beginning with several class action suits filed in late 1999 against managed care companies by aggrieved HMO enrollees, and continuing with government suits against the paint and handgun industries, this new form of litigation has become a powerful vehicle for plaintiffs to punish unpopular--but entirely legal--industries. In this Note, the author demonstrates that the popular appeal of these suits conceals legal theories of recovery that probably could not survive courtroom scrutiny. The author argues that the thin legal merits of these class action claims are often tolerated by courts, who urge settlement in order to clear their dockets, and by the industries, who regard settlement merely as a cost of doing business. The author concludes that the tobacco litigation and its progeny encourage citizens and the executive branches of government to seek restitution and fundamental social change in the courts after losing in the legislative arena, thus forcing the judiciary branches into the unwise and improper role of policymaker.

Delivery of Health Care↗
PubMed1976

Laboratory investigation of "biorhythms".

Three subjects were tested on an information processing task on a daily basis for a period of 70 d. Performance measurement included reaction time, movement time, and information processing rate. The data set obtained was subjected to Fast Fourier Transforms (FFT) in an attempt to identify periodicities in performance. Twelve significant harmonics were identified and nine were found to be within 1 d of at least one of the cycles hypothesized by the theory of "biorhythms." The probability of this occurring by chance is remote (p less than 0.05), assuming a uniform distribution of significant amplitude. The results were interpreted as suggesting the possibility of a biorhythmic influence in the performance of the task.

Adult↗
PubMed2006

[The connection between hospital volume and outcome in thorax surgery].

A review of current literature with respect to a possible correlation among hospital volume, caseload and outcome of thoracic and cardiovascular surgery supports quite convincingly the theory that, from a probability point of view, the combination of high-volume hospitals with high-volume surgeons produces the best results. During the last decade, thoracic and cardiovascular surgery has to a certain degree been centralized in Denmark, reducing the number of public centres to the five university hospitals. None of these centres is low-volume, and two are high-volume hospitals.

Cardiovascular Surgical Procedures↗
PubMedDate not supplied

[Adamantinoma from odontogenic cysts].

The observation of an adamantinoma's case propped up an odontogenic cyst to check the complicated histogenic problem connected to this eventuality. After considering several theories they suppose a probable derivation from the odontogenic epithelium that has undoubted potentiality.

Adult↗
PubMedDate not supplied

[The organization of time in biological systems].

A notion of organization of time similar to the notion of organization of space in architecture has been introduced. The level and pattern of organization of time in biological systems differs from that in physical and chemical systems, which presents an independent problem. Analysis of the problem leads to a new definition of life as a process of renormalization of possibilities described by a Bayes formula. This definition leads to the notion of self-monitoring as a property of every biological system, and of complicated structure of the biological present, including the physical past and physical future. This is naturally followed by determination by far past, and, hence, memory, and determination by future, i.e. preadaptation, surpassing reflection, aim-setting etc. A direct dependence of a number of elements of a complex system on its stability has been demonstrated. The self-monitoring and organization of time can be traced at various levels of biological hierarchy from intracellular to biosphere level.

Animals↗
PubMed1989

[Cyclothymia ending in dementia. A case report].

Three cases of manic-depressive illness are presented which, with various manifestations of pseudodementia, end in dementia. The relationship of cyclothymia to dementia is discussed, and the need for diagnosis with the aid of equipment is stressed. Notwithstanding the absence of systematic theories, it seems most probable that senile dementia (Alzheimer dementia) may be associated with cyclothymia.

Aged↗
PubMed1986

Renewal theory, Geiger counters, and the maximum number of receptors bound to a randomly haptenated polymer chain.

Polymers containing small chemical groups (haptens) covalently attached at random along the chain are commonly used to initiate an immune response. Properties of the polymer such as its length, the spacing of the haptens, and the total number of haptens along the chain, correlate with its immune reactivity. Here we model the ability of many finite-sized cell surface receptors to bind simultaneously the haptens conjugated to a polymer chain. The binding sites on two different receptors or on separate parts of a multivalent receptor cannot be arbitrarily close to one another; so, in general, not all haptens along a polymer chain can be simultaneously bound by receptors. We develop an analogy between the steric hindrance among receptors detecting randomly placed haptens and the temporary locking of a Geiger counter that has detected a radioactive decay. Using renewal theory, we compute the probability distribution, and its moments, for the maximum number of haptens that can be simultaneously bound by monovalent receptors. We also model flexible bivalent receptors and obtain the mean and variance of the maximum number of receptors bound to randomly haptenated polymers, and the mean and variance of the maximum number of haptens bound. We demonstrate the importance of our results by applying them to immunological data and showing that, for polymers used in immunology, the effective valence of a polymer may be as much as 50% smaller than its nominal valence.

Biopolymers↗