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PubMedDate not supplied

[Elements of probability calculation. I].

This is the first of a series of articles on probability calculation, consisting of a simple introduction to the definitions of probability. A brief historical background explains some of the reasons for the delay in the development of probability calculation and recalls the main problems that had to be faced, the solution of which marked the birth of the theory of probability. Classical, frequentist and subjective approaches are addressed and their relative merits and weaknesses are discussed.

Probability↗

PubMed1989

Children's ability to make probability estimates: skills revealed through application of Anderson's functional measurement methodology.

Functional measurement methodology was used to assess children's attention to the total number of alternative outcomes as well as the number of target outcomes when making probability estimates. In Study 1, first-, third-, and fifth-grade children were given the task of estimating on a simple, continuous but nonnumeric scale the probability of drawing a particular color of jelly bean from a bag containing either 1, 2, or 3 jelly beans of that color, and either 6, 8, or 10 jelly beans total. In Study 2, first- through fifth-grade children were given the task of estimating the likelihood that a bug would fall on a pot containing a flower when presented displays of planters containing either 2, 3, 4, or 5 pots with flowers, and 6, 8, or 10 pots total. In both studies, the children were exposed to each of the combinations of numerator and denominator across 3 replications. The results indicate that all age groups attend to variations in the denominator as well as to variations in the numerator, and, furthermore, that they attend to the interaction between these variables. This finding contrasts sharply with research that requires children to choose which of 2 containers offers the greater chance of yielding a target item in a blind draw. It is suggested that children possess the skill to make accurate probability estimates, but they are unaware that these estimates should always be made and used when comparing the probability of an event across trials. The findings are discussed in relation to the broader issue of the limitations of the choice paradigm as a means of investigating children's thinking.

Attention↗

PubMed1989

Clinical outcome of patients with a 'low probability' of pulmonary embolism on ventilation-perfusion lung scan.

Lung ventilation and perfusion (V/Q) scintigraphy is usually indicated when pulmonary embolism (PE) is a suspected diagnosis. Typically, V/Q scintigraphic interpretation is reported as a "normal," "low," "intermediate," or "high probability" of PE. Although a "low probability" interpretation does not exclude the diagnosis of PE, it significantly reduces the likelihood. We retrospectively analyzed up to one year of follow-up in 90 patients who were clinically suspected of having PE, but in whom V/Q scintigraphy implied a low probability of PE. None of the 90 patients demonstrated clinical evidence of PE subsequent to the V/Q scan. Our findings suggest that significant pulmonary embolism is uncommon and that the clinical course appears to be predictable in patients with a low probability V/Q scan.

Follow-Up Studies↗

PubMedDate not supplied

Mycoplasma meleagridis of turkeys: probability of eliminating egg-borne infection.

An equation was developed that describes the probability of eliminating egg-borne Mycoplasma meleagridis (MM) of turkeys by egg treatment. Probability (P) of MM elimination was described in terms of four parameters: pretreatment prevalence of MM, alpha; treatment failure rate, beta; number of eggs treated, n; and hatching rate, h. The eradication equation, based on the Poisson probability distribution, was P(0) = e-n alpha beta h. Probabilities derived from 12 hypothetical MM-eradication situations showed that increasing the size of any or all of the parameters decreased the likelihood of eradication. Use of the predictive equation as a planning tool in a successful MM-eradication program is demonstrated.

Animals↗

PubMed1987

Varying probability of the development of acute nonlymphoblastic leukemia in refractory anemia patients with an excess of blasts.

The cumulative leukemia-free survival rate of refractory anemia with excess of blasts was fitted to three parametric failure time models, i.e., the usual exponential and Weibull, and exponential mixture models. Among the three, the best fit model was the exponential mixture model, which was 119 times more likely to assume that samples came from the exponential mixture distribution than to assume that those were from the usual Weibull distribution. This strongly suggests that refractory anemia with excess of blasts consists of subgroups with very high and very low probability to develop acute nonlymphoblastic leukemia. The estimated proportion of the very low probability group was about 30%. Analysis by the exponential mixture model with covariates revealed that the probability of a patient to develop acute nonlymphoblastic leukemia could be estimated by three covariates, i.e., bone marrow blast percentage; abnormal granules of granulocytes; and mononuclear large megakaryocytes. The estimated probabilities ranged from 17 to 99%, according to the model.

Acute Disease↗

PubMed1985

Complication probability as assessed from dose-volume histograms.

Optimization of a treatment plan for radiation therapy will produce a plan with the highest probability for tumor control without exceeding an acceptable complication rate. To achieve this goal it is necessary to have a means to estimate probabilities of local control and normal tissue complication. In general, good treatment plans deliver a high uniform dose to the target volume and lower doses to the surrounding normal tissues. The tolerance dose values available for various normal tissues are usually assumed to apply to partial or full volumes of the tissue which have been uniformly irradiated. These values are the best guidelines for estimating complication probabilities in tissues that receive a uniform dose to a fraction of the tissue and no dose to the remainder. Dose-volume histograms are one means of evaluating the uniformity of the irradiation on the tissues. Frequently the normal tissues are not uniformly irradiated as is demonstrated by dose-volume histograms for different treatment plans. A recursive algorithm which uses these tolerance dose data has been written and can be applied to arbitrary dose-volume histograms to estimate the complication probability.

Dose-Response Relationship, Radiation↗

PubMed1985

The accuracy of experienced physicians' probability estimates for patients with sore throats. Implications for decision making.

Ten physicians recorded their treatment decisions and estimated probabilities of streptococcal infection for patients with sore throats. Of 308 throat cultures, 15 (4.9%) were positive for group A streptococci. The physicians overestimated the probability of a positive culture for 81% of their patients and their estimates and treatment decisions were strongly associated. Of 104 patients treated before culture results were available, only eight had positive cultures. Probability overestimation may have been due to neglect of the low culture-positive rate, assignment of undue importance to weakly predictive or highly intercorrelated clinical features, and a value-induced bias, occurring when features important for treatment are erroneously linked to the likelihood of disease. Cognitive limitations in information processing may limit the effectiveness of pharyngitis management protocols that require subjective estimates of disease probability.

Adolescent↗

PubMed1985

Probability-reward preferences of rhesus monkeys.

The relative preferences of rhesus monkeys for reward probability versus amount were investigated with procedures which contrasted general experience with specific instructions, and evaluated the relationship between probability-amount combinations and preference strength. Four stimulus objects, each signifying a different combination of reward frequency and amount (100% with one unit; 50% with two units; 33% with three units; or 25% with four units), were presented in pairs, one pair per daily session, with trial schedules providing the same amount of reward within each set of 12 trials. In Phase A, 4 monkeys (Group 1) were tested on the six choice-pairs with no preliminary training. In Phase B, Group 1 was joined by an additional 4 monkeys (Group 2), and each of the tasks was preceded by a demonstration of the relevant stimuli, one at a time, together with their associated probabilities and amounts. Group 1 animals developed preferences during Phase A for the more frequently rewarded objects, which persisted into Phase B, whereas Group 2 animals showed no preferences. This result indicates that preliminary instructions concerning the reward combinations associated with stimulus objects can prevent the development of a preference for greater probability over greater amount of reward, but cannot extinguish it once it has been formed or reestablished within the context of a particular task.

Animals↗

PubMed1984

Some fallacies in the computation of paternity probabilities.

Legal identification of fathers by means of a "paternity probability" has been used in European courts for decades, and has recently been introduced into American courts and accepted by some of them. The voluminous literature on this topic contains virtually no fundamental criticism of the logical basis for the probabilistic computations. Here I suggest that the "paternity probability" suffers from three basic fallacies: (1) contrary to claims, the figure is not, in fact, the probability that the alleged father is the true father, (2) the denominator of the likelihood ratio used in the computation is driven by (sometimes self-contradictory) assumptions and is not based on facts, and (3) post-inclusionary computations are based on speculation about genotypes that does not constitute scientific evidence. It is recommended that pending the resolution of these difficulties "paternity probabilities" should not be computed or introduced as positive evidence of paternity.

Bayes Theorem↗

PubMed1983

[Decision strategy: effect of probability of the results and of the allowed time on choice reaction time and on movement time].

In many sport activities, the speed with which a performer can complete the required response is an important determinant of performance. In order to minimize this time an individual can initiate and execute the response faster. A number of studies (Alain & Proteau, 1977; Proteau & Dugas, 1982; Régnier & Salmela, 1980) in which individual was to move for two meters in a choice reaction time task have shown that, when the probability of one of the two events was 0,9, the movement time (MT) was significantly reduced. The results may perhaps be explained by the fact that subjects shifted their weight during the foreperiod (FP) preceding the stimulus and then facilitated the movement execution (reflected by a lower MT). The present experiment was designed to test the second possibility. Subjects initiated their responses from a dynamographic platform. The independent variables were the probabilities of the two events and the time allowed for subjects to complete the response. Results indicated that when the probability of one of the two events was sufficiently high (0,9), subjects did shift their weight during the FP in order to produce a faster response. The results supported the fact that subjects, in sport like situations, prepare themselves, at least partially, but only when the probability of the event is very high.

Decision Making↗

PubMed1980

Second-order approximations of ascertainment probabilities.

A second-order correction is derived for the usual first-order order approximation to the probability of ascertaining a pedigree. Both the first- and second-order approximations are compared to the exact ascertainment probability for selected examples of monogenic and polygenic traits. The second-order approximation is shown to be accurate within 10% when the individual ascertainment probability is less than 0.2, for most cases examined. In all cases, the first- and second-order approximations provide upper and lower bounds, respectively, for the exact ascertainment probability.

Humans↗

PubMedDate not supplied

Mathematical modeling of intracellular transport processes and the creatine kinase systems: a probability approach.

A probability approach was used to describe mitochondrial respiration in the presence of substrates, ATP, ADP, Cr and PCr. Respiring mitochondria were considered as a three-component system, including: 1) oxidative phosphorylation reactions which provide stable ATP and ADP concentrations in the mitochondrial matrix; 2) adenine nucleotide translocase provides exchange transfer of matrix adenine nucleotides for those from outside, supplied from medium and by creatine kinase; 3) creatine kinase, starting these reactions when activated by the substrates from medium. The specific feature of this system is close proximity of creatine kinase and translocase molecules. This results in high probability of direct activation of translocase by creatine kinase-derived ADP or ATP without their leak into the medium. In turn, the activated translocase with the same high probability directly provides creatine kinase with matrix-derived ATP or ADP. The catalytic complexes of creatine kinase formed with ATP from matrix together with those formed from medium ATP provide activation of the forward creatine kinase reaction coupled to translocase activation. Simultaneously the catalytic complexes of creatine kinase formed with ADP from matrix together with those formed from medium ADP provide activation of the reverse creatine kinase reaction coupled to translocase activation. The considered probabilities were arranged into a mathematical model. The model satisfactorily simulates the available experimental data by several groups of investigators. The results allow to consider the observed kinetic and thermodynamic irregularities in behavior of structurally bound creatine kinase as a direct consequence of its tight coupling to translocase.

Adenine Nucleotides↗

PubMed1995

Customized probability models for early severe sepsis in adult intensive care patients. Intensive Care Unit Scoring Group.

OBJECTIVE: To develop customized versions of the Simplified Acute Physiology Score II (SAPS II) and the 24-hour Mortality Probability Model II (MPM II) to estimate the probability of mortality for intensive care unit patients with early severe sepsis. DESIGN AND SETTING: Logistic regression models developed for patients with severe sepsis in a database of adult medical and surgical intensive care units in 12 countries. PATIENTS: Of 11,458 patients in the intensive care unit for at least 24 hours, 1130 had severe sepsis based on criteria of the American College of Chest Physicians and the Society of Critical Care Medicine (systemic inflammatory response syndrome in response to infection, plus hypotension, hypoperfusion, or multiple organ dysfunction). RESULTS: In patients with severe sepsis, mortality was higher (48.0% vs 19.6% among other patients) and 28-day survival was lower. The customized SAPS II was well calibrated (P = .92 for the goodness-of-fit test) and discriminated well (area under the receiver operating characteristic [ROC] curve, 0.78). Performance in the validation sample was equally good (P = .85 for the goodness-of-fit test; area under the ROC curve, 0.79). The customized MPM II was well calibrated (P = .92 for the goodness-of-fit test) and discriminated well (area under the ROC curve, 0.79). Performance in the validation sample was equally good (P = .52 for the goodness-of-fit test; area under the ROC curve, 0.75). The models are independent of each other; either can be used alone to estimate the probability of mortality of patients with severe sepsis. CONCLUSIONS: Customization provides a simple technique to apply existing models to a subgroup of patients. Accurately assessing the probability of hospital mortality is a useful adjunct for clinical trials.

Adult↗

PubMed1994

Effects of target probability and memory demands on the vigilance of adults with and without mental retardation.

The vigilance of young adults with mild mental retardation and without mental retardation was compared in two experiments in which observers performed two memory demanding, cognitively based, 60-minute tests. In Experiment 1, target probability was 5% or 30% with a 1.5-second event rate. Detection by observers with mental retardation declined more rapidly than did that of observers without mental retardation in both target probability conditions; further, their response criterion became increasingly more conservative. In Experiment 2, target probability was 10% or 30% with an 8-second event rate. Observers with mental retardation detected fewer targets under both target probability conditions. Subjects' response criterion differed as a function of level of intelligence from the onset of the vigil and did not change with time on task. Intelligence-related differences in vigilance were explained in terms of subjects' information-processing abilities.

Adolescent↗

PubMed1993

A single-gene explanation for the probability of having idiopathic talipes equinovarus.

It has been hypothesized that the pathogenesis of idiopathic talipes equinovarus (ITEV, or clubfoot) is explained by genetic regulation of development and growth. The objective of the present study was to determine whether a single Mendelian gene explains the probability of having ITEV in a sample of 143 Caucasian pedigrees from Iowa. These pedigrees were ascertained through probands with ITEV. Complex segregation analyses were undertaken using a regressive logistic model. The results of these analyses strongly rejected the hypotheses that the probability of having ITEV in these pedigrees was explained by a non-Mendelian pattern of transmission with residual sibling correlation, a nontransmitted (environmental) factor with residual sibling correlation, or residual sibling correlation alone. These results were consistent with the hypothesis that the probability of having ITEV was explained by the Mendelian segregation of a single gene with two alleles plus the effects of some unmeasured factor(s) shared among siblings. The segregation of alleles at this single Mendelian gene indicated that the disease allele A was incompletely dominant to the nondisease allele B. The disease allele A, associated with ITEV affection, was estimated to occur in the population of inference with a frequency of .007. After adjusting for sex-specific population incidences of ITEV, the conditional probability (penetrance) of ITEV affection given the AA, AB, and BB genotypes was computed to be 1.0, .039, and .0006, respectively. Individual pedigrees in this sample that most strongly supported the single Mendelian gene hypothesis were identified. These pedigrees are candidates for genetic linkage analyses or DNA association studies.

Clubfoot↗

PubMedDate not supplied

[The dynamics of individual preference in the probability and value of reinforcement in the development of experimental neurosis].

After single and repeated negative emotiogenic (neuroticizing) influences in phlegmatics and cholerics in a situation with different probability and value of reinforcement a change of behaviour strategy takes place--from the preference of a reinforcement of higher probability but worse quality to that of low probability but valuable. Strategy of behaviour of sanguinics and melancholics remains unchanged with the preference of a reinforcement of low probability but better quality. The greatest sensibility to negative emotiogenic influence (a conflict situation) was established in phlegmatics and the lowest sensibility--in sanguinics. The obtained data are discussed from the positions of P. V. Simonov's concept on the four brain macrostructures (the hippocampus, amygdala, hypothalamus, and the frontal cortex) in the aspect of significance of the level of their functioning and interaction for the pathogenesis of neuroses.

Animals↗

PubMedDate not supplied

Hypersensitivity reactions to drugs: correlation between clinical probability score and laboratory diagnostic procedures.

The in vitro diagnosis of allergic drug reactions have not made significant progress in recent years. Specific stimulation of lymphocytes from allergic patients represents an approach to demonstrating sensitization to the implicated drug. So far, skin tests and RAST can only be applied to a limited number of situations. The purpose of this study was to standardize the clinical criteria in order to establish a clinical probability score for each drug. Independently, the various laboratory procedures mentioned were compared with the established clinical probability score for each drug. The results showed that, for the few common drugs studied, the correlation between the clinical probability score and the results of the in vitro lymphocyte transformation test was significant. A significant correlation between the clinical probability score and the skin tests was only shown for penicillin and its derivatives.

Drug Hypersensitivity↗

PubMed1996

[Paternity probability in the cases of incest].

To calculate the paternity probability in the cases of incest where the alleged father was either the father or the brother of the plaintiff's mother, some algebraic expressions applicable to a simple codominant diallelic genetic marker system were derived by modifying the formulas of Essen-Möller and Komatsu (the both formulas gave the same result). The paternity probability in the incest case is generally lower than that in usual case, because in the former case an allele present in the mother is sometimes found in both the alleged father and the child (plaintiff), even if the alleged father is not true father. The paternity probability in the incest case, however, becomes higher than that in usual case when an allele is common to both the alleged father and the child but not to the mother. The mean value of paternity probability becomes lower, as the relationship becomes closer between the alleged father and the mother.

Alleles↗