Probability Estimates for Petroleum Drilling Decisions

1974 ◽  
Vol 26 (06) ◽  
pp. 687-695 ◽  
Author(s):  
Marvin B. Smith
Keyword(s):  
Probability Estimates ◽  
Petroleum Drilling

Utilisation of Lasers in Petroleum Drilling Industry

2013 ◽  
Author(s):  
M. Bazargan ◽  
A. Madani ◽  
H. Sharifi ◽  
H. Jalalyfar ◽  
K. Ghassemal askary ◽  
...  
Keyword(s):  
Petroleum Drilling

scholarly journals Using body temperature and variables commonly available in the EHR to predict acute infection: a proof-of-concept study showing improved pretest probability estimates for acute COVID-19 infection among discharged emergency department patients

Diagnosis ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Carl T. Berdahl ◽  
An T. Nguyen ◽  
Marcio A. Diniz ◽  
Andrew J. Henreid ◽  
Teryl K. Nuckols ◽  
...  
Keyword(s):  
Emergency Department ◽  
Body Temperature ◽  
Acute Infection ◽  
Time Of Day ◽  
Pretest Probability ◽  
Absolute Difference ◽  
Proof Of Concept ◽  
Easy Method ◽  
Concept Study ◽  
Probability Estimates

Abstract Objectives Obtaining body temperature is a quick and easy method to screen for acute infection such as COVID-19. Currently, the predictive value of body temperature for acute infection is inhibited by failure to account for other readily available variables that affect temperature values. In this proof-of-concept study, we sought to improve COVID-19 pretest probability estimation by incorporating covariates known to be associated with body temperature, including patient age, sex, comorbidities, month, and time of day. Methods For patients discharged from an academic hospital emergency department after testing for COVID-19 in March and April of 2020, we abstracted clinical data. We reviewed physician documentation to retrospectively generate estimates of pretest probability for COVID-19. Using patients’ COVID-19 PCR test results as a gold standard, we compared AUCs of logistic regression models predicting COVID-19 positivity that used: (1) body temperature alone; (2) body temperature and pretest probability; (3) body temperature, pretest probability, and body temperature-relevant covariates. Calibration plots and bootstrap validation were used to assess predictive performance for model #3. Results Data from 117 patients were included. The models’ AUCs were: (1) 0.69 (2) 0.72, and (3) 0.76, respectively. The absolute difference in AUC was 0.029 (95% CI −0.057 to 0.114, p=0.25) between model 2 and 1 and 0.038 (95% CI −0.021 to 0.097, p=0.10) between model 3 and 2. Conclusions By incorporating covariates known to affect body temperature, we demonstrated improved pretest probability estimates of acute COVID-19 infection. Future work should be undertaken to further develop and validate our model in a larger, multi-institutional sample.

FORWARD APPORTIONMENT OF CENSORED COUNTS FOR DISCRETE NONPARAMETRIC MAXIMUM LIKELIHOOD ESTIMATION OF FAILURE PROBABILITIES

2009 ◽  
Vol 16 (03) ◽  
pp. 213-234
Author(s):  
MINNIE H. PATEL ◽  
H.-S. JACOB TSAO
Keyword(s):  
Maximum Likelihood ◽  
Maximum Likelihood Estimation ◽  
Closed Form ◽  
Failure Probability ◽  
Likelihood Estimation ◽  
Lifetime Distribution ◽  
Nonparametric Maximum Likelihood ◽  
Kaplan Meier ◽  
Probability Estimates ◽  
Failure Probabilities

Empirical cumulative lifetime distribution function is often required for selecting lifetime distribution. When some test items are censored from testing before failure, this function needs to be estimated, often via the approach of discrete nonparametric maximum likelihood estimation (DN-MLE). In this approach, this empirical function is expressed as a discrete set of failure-probability estimates. Kaplan and Meier used this approach and obtained a product-limit estimate for the survivor function, in terms exclusively of the hazard probabilities, and the equivalent failure-probability estimates. They cleverly expressed the likelihood function as the product of terms each of which involves only one hazard probability ease of derivation, but the estimates for failure probabilities are complex functions of hazard probabilities. Because there are no closed-form expressions for the failure probabilities, the estimates have been calculated numerically. More importantly, it has been difficult to study the behavior of the failure probability estimates, e.g., the standard errors, particularly when the sample size is not very large. This paper first derives closed-form expressions for the failure probabilities. For the special case of no censoring, the DN-MLE estimates for the failure probabilities are in closed forms and have an obvious, intuitive interpretation. However, the Kaplan–Meier failure-probability estimates for cases involving censored data defy interpretation and intuition. This paper then develops a simple algorithm that not only produces these estimates but also provides a clear, intuitive justification for the estimates. We prove that the algorithm indeed produces the DN-MLE estimates and demonstrate numerically their equivalence to the Kaplan–Meier-based estimates. We also provide an alternative algorithm.

Cost-Effectiveness Study of the Extracorporeal Shock-Wave Lithotriptor

1990 ◽  
Vol 6 (4) ◽  
pp. 623-632 ◽  
Author(s):  
Evi E. Hatziandreu ◽  
Karen Carlson ◽  
Albert G. Mulley ◽  
Milton C. Weinstein
Keyword(s):  
Shock Wave ◽  
Cost Effectiveness ◽  
Meta Analysis ◽  
Time Frame ◽  
Upper Urinary Tract ◽  
Extracorporeal Shock Wave ◽  
Probability Estimates ◽  
Urinary Tract Stones ◽  
Ultrasonic Lithotripsy ◽  
Cost Effectiveness Study

AbstractWe performed a cost-effectiveness analysis to examine the relative efficacy and costs of percutaneous ultrasonic lithotripsy (PUL), extracorporeal shock-wave lithotripsy (ESWL), and surgery for the treatment of upper urinary tract stones. We developed a Markov model with 35 states, cycles of 3 months, and a time frame of 5 years. Probability estimates were derived from a meta-analysis of the published literature. For stones less than or equal to 2 cm, ESWL is preferred to PUL, since it prevents 2 additional days of morbidity and saves $440. For larger stones, PUL is preferable to ESWL, avoiding 4 more days of morbidity, and saving $722. Both ESWL and PUL were superior to surgery. Sensitivity analysis showed that the results are sensitive to ESWL efficacy rates, the stone recurrence rate, and the hospital component of the ESWL cost. Our analysis suggests that although ESWL is preferable, relatively small changes in the efficacy and cost can shift the preferred strategy; in addition, these findings underscore the need for more reliable data.

SOME TRAFFIC SAFETY ISSUES AT UNREGULATED PEDESTRIAN CROSSINGS IN THE CITY

2021 ◽  
Vol 5 (12(81)) ◽  
pp. 26-32
Author(s):  
V. Volkov ◽  
E. Nabatnikova ◽  
E. Lebedev
Keyword(s):  
Traffic Safety ◽  
Traffic Accident ◽  
Traffic Accidents ◽  
Road Traffic ◽  
Hourly Interval ◽  
Safety Issues ◽  
The Road ◽  
Probability Estimates ◽  
Mode Of Transport ◽  
Speed Mode

The groups of participants of the pedestrian and automobile flows, whose actions cause the greatest danger to the occurrence of conflict situations in the zone of unregulated transition, are identified. The factors determining the likelihood of a traffic accident at an unregulated transition are systematized, for which probability estimates of the occurrence of road traffic accidents are calculated. As an estimated parameter, the hazard coefficient of a conflict point of an unregulated transition is proposed, which is determined by the ratio of the probability of a traffic accident in the real-time hourly interval to the average annual probability of a traffic accident reduced to the hourly interval. The dependences of the hazard ratio of an unregulated transition are established on the most significant factors: the speed mode of transport in the area before the transition and the state of the road surface.

Pipeline Geohazard Assessment: Bridging the Gap Between Integrity Management and Construction Safety Contexts

2018 ◽  
Author(s):  
Rodney S. Read
Keyword(s):  
Construction Safety ◽  
Worker Safety ◽  
Ground Movement ◽  
Pipeline Construction ◽  
Probability Estimates ◽  
Subject Matter Expertise ◽  
Management Context ◽  
Integrity Management ◽  
Geohazard Assessment

Geohazards are threats of a geological, geotechnical, hydrological, or seismic/tectonic nature that may negatively affect people, infrastructure and/or the environment. In a pipeline integrity management context, geohazards are considered under the time-independent threat category of Weather-related and Outside Force in the American standard ASME B31.8S. Geotechnical failure of pipelines due to ground movement is addressed in Annex H and elsewhere in the Canadian standard CSA-Z662. Both of these standards allow flexibility in terms of geohazard assessment as part of pipeline integrity management. As a result of this flexibility, many systems for identifying, characterizing, analyzing and managing geohazards have been developed by operators and geotechnical engineering practitioners. The evolution of these systems, and general expectations regarding geohazard assessment, toward quantitative geohazard frequency assessment is a trend in recent pipeline hearings and regulatory filings in Canada. While this trend is intended to frame geohazard assessment in an objective and repeatable manner, partitioning the assessment into a series of conditional probability estimates, the reality is that there is always an element of subjectivity in assigning these conditional probabilities, requiring subject matter expertise and expert judgment to make informed and defensible decisions. Defining a specific risk context (typically loss of containment from a pipeline) and communicating uncertainty are important aspects of applying these types of systems. Adoption of these approaches for alternate risk contexts, such as worker safety during pipeline construction, is challenging in that the specific geohazards and threat scenarios considered for long-term pipeline integrity may or may not adequately represent all credible threats during pipeline construction. This paper explores the commonalities and differences in short- and long-term framing of geohazard assessment, and offers guidance for extending geohazard assessment for long-term pipeline integrity to other contexts such as construction safety.

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