scholarly journals Comparative statistical analysis of simulated ice management effectiveness

2019 ◽  
Vol 2 (1) ◽  
pp. 79-91
Author(s):  
Amy Price ◽  
Maria Yulmetova ◽  
Sarah Khalil
Keyword(s):  
Confidence Intervals ◽  
Probability Distributions ◽  
Management Effectiveness ◽  
Distribution Fitting ◽  
Management Performance ◽  
Distance Ratio ◽  
The Mean ◽  
Comparative Statistical Analysis ◽  
Level Of Experience ◽  
The Impact

AbstractIce management is critical for safe and efficient operations in ice-covered waters; thus, it is important to understand the impact of the operator’s experience in effective ice management performance. This study evaluated the confidence intervals of the mean and probability distributions of two different sample groups, novice cadets and experienced seafarers, to evaluate if there was a difference in effective ice management depending on the operator’s level of experience. The ice management effectiveness, in this study, is represented by the “clearing-to-distance ratio” that is the ratio between the area of cleared ice (km2) and the distance travelled by an ice management vessel (km) to maintain that cleared area. The data analysed in this study was obtained from a recent study conducted by Memorial University’s “Safety at Sea” research group. With the distribution fitting analysis providing inconclusive results regarding the normality of the data, the confidence intervals of the dataset means were obtained using both parametric approaches, such as t-test, Cox’s method, and Johnson t-approach, and non-parametric methods, namely Jackknife and Bootstrap methods, to examine if the assumption of normality was valid. The comparison of the obtained confidence interval results demonstrates that the mean efficiency of the cadets is more consistent, while it is more varied among seafarers. The noticeable difference in ice management performance between the cadet and seafarer sample groups is revealed, thus, proving that crew experience positively influences ice management effectiveness.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

scholarly journals Design impact and significance of non-stationarity of variance in extreme rainfall

2015 ◽  
Vol 371 ◽  
pp. 117-123 ◽  
Author(s):  
M. Al Saji ◽  
J. J. O'Sullivan ◽  
A. O'Connor
Keyword(s):  
Confidence Intervals ◽  
Goodness Of Fit ◽  
Daily Rainfall ◽  
Trend Detection ◽  
Climate Change Signal ◽  
Annual Maximum ◽  
Important Indicator ◽  
Detection Techniques ◽  
The Mean ◽  
The Impact

Abstract. Stationarity in hydro-meteorological records is often investigated through an assessment of the mean value of the tested parameter. This is arguably insufficient for capturing fully the non-stationarity signal, and parameter variance is an equally important indicator. This study applied the Mann-Kendall linear and Mann-Whitney-Wilcoxon step change trend detection techniques to investigate the changes in the mean and variance of annual maximum daily rainfalls at eight stations in Dublin, Ireland, where long and high quality daily rainfall records were available. The eight stations are located in a geographically similar and spatially compact region (< 950 km2) and their rainfalls were shown to be well correlated. Results indicate that while significant positive step changes were observed in mean annual maximum daily rainfalls (1961 and 1997) at only two of the eight stations, a significant and consistent shift in the variance was observed at all eight stations during the 1980's. This period saw a widely noted positive shift in the winter North Atlantic Oscillation that greatly influences rainfall patterns in Northern Europe. Design estimates were obtained from a frequency analysis of annual maximum daily rainfalls (AM series) using the Generalised Extreme Value distribution, identified through application of the Modified Anderson Darling Goodness of Fit criterion. To evaluate the impact of the observed non-stationarity in variance on rainfall design estimates, two sets of depth-frequency relationships at each station for return periods from 5 to 100-years were constructed. The first was constructed with bootstrapped confidence intervals based on the full AM series assuming stationarity and the second was based on a partial AM series commencing in the year that followed the observed shift in variance. Confidence intervals distinguish climate signals from natural variability. Increases in design daily rainfall estimates obtained from the depth-frequency relationship developed from the truncated AM series, as opposed to those using the full series, ranged from 5 to 16% for the 5-year event and from 20 to 41% for the 100-year event. Results indicate that the observed trends exceed the envelopes of natural climate variability and suggest that the non-stationarity in variance is associated with a climate change signal. Results also illustrate the importance of considering trends in higher order moments (e.g. variance) of hydro-meteorological variables in assessing non-stationarity influences.

scholarly journals Analysis of a Discrete-Time Queueing Model with Disasters

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3283
Author(s):  
Mustafa Demircioglu ◽  
Herwig Bruneel ◽  
Sabine Wittevrongel
Keyword(s):  
Discrete Time ◽  
Queueing System ◽  
Time Slot ◽  
Probability Distributions ◽  
Single Server ◽  
Bernoulli Process ◽  
Tail Probabilities ◽  
Mean Values ◽  
The Mean ◽  
The Impact

Queueing models with disasters can be used to evaluate the impact of a breakdown or a system reset in a service facility. In this paper, we consider a discrete-time single-server queueing system with general independent arrivals and general independent service times and we study the effect of the occurrence of disasters on the queueing behavior. Disasters occur independently from time slot to time slot according to a Bernoulli process and result in the simultaneous removal of all customers from the queueing system. General probability distributions are allowed for both the number of customer arrivals during a slot and the length of the service time of a customer (expressed in slots). Using a two-dimensional Markovian state description of the system, we obtain expressions for the probability, generating functions, the mean values, variances and tail probabilities of both the system content and the sojourn time of an arbitrary customer under a first-come-first-served policy. The customer loss probability due to a disaster occurrence is derived as well. Some numerical illustrations are given.

scholarly journals The Importance of Accounting for Parameter Uncertainty in SF-6D Value Sets and Its Impact on Studies that Use the SF-6D to Measure Health Utility

2020 ◽  
Vol 17 (11) ◽  
pp. 3949
Author(s):  
Samer A. Kharroubi ◽  
Yara Beyh ◽  
Esmail Abdul Fattah ◽  
Tracey Young
Keyword(s):  
Confidence Intervals ◽  
Bayesian Approach ◽  
Parameter Uncertainty ◽  
Economic Evaluations ◽  
Value Set ◽  
Study Results ◽  
Valuation Study ◽  
The Mean ◽  
Value Sets ◽  
The Impact

Background: The parameter uncertainty in the six-dimensional health state short form (SF-6D) value sets is commonly ignored. There are two sources of parameter uncertainty: uncertainty around the estimated regression coefficients and uncertainty around the model’s specification. This study explores these two sources of parameter uncertainty in the value sets using probabilistic sensitivity analysis (PSA) and a Bayesian approach. Methods: We used data from the original UK/SF-6D valuation study to evaluate the extent of parameter uncertainty in the value set. First, we re-estimated the Brazier model to replicate the published estimated coefficients. Second, we estimated standard errors around the predicted utility of each SF-6D state to assess the impact of parameter uncertainty on these estimated utilities. Third, we used Monte Carlo simulation technique to account for the uncertainty on these estimates. Finally, we used a Bayesian approach to quantifying parameter uncertainty in the value sets. The extent of parameter uncertainty in SF-6D value sets was assessed using data from the Hong Kong valuation study. Results: Including parameter uncertainty results in wider confidence/credible intervals and improved coverage probability using both approaches. Using PSA, the mean 95% confidence intervals widths for the mean utilities were 0.1394 (range: 0.0565–0.2239) and 0.0989 (0.0048–0.1252) with and without parameter uncertainty whilst, using the Bayesian approach, this was 0.1478 (0.053–0.1665). Upon evaluating the impact of parameter uncertainty on estimates of a population’s mean utility, the true standard error was underestimated by 79.1% (PSA) and 86.15% (Bayesian) when parameter uncertainty was ignored. Conclusions: Parameter uncertainty around the SF-6D value set has a large impact on the predicted utilities and estimated confidence intervals. This uncertainty should be accounted for when using SF-6D utilities in economic evaluations. Ignoring this additional information could impact misleadingly on policy decisions.

A Cross Sectional Observational Study to Assess Pharmacists Perspective and General Health Wellbeing During COVID-19 Pandemic in Saudi Arabia

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Nagwa Ibrahim ◽  
Asma Almuhsin ◽  
Raghad Alkhattabi ◽  
Maryam Almulaifi ◽  
Ali Alrumaih
Keyword(s):  
Saudi Arabia ◽  
Observational Study ◽  
General Health ◽  
Negative Impact ◽  
Eastern Region ◽  
Knowledge Level ◽  
Cross Sectional ◽  
The Mean ◽  
Level Of Experience ◽  
The Impact

Introduction: COVID-19 pandemic impacted all countries negatively. Regulatory bodies in Saudi Arabia and worldwide set a firm policies and guidelines to protect their nationals and residents from the virus. Pharmacists play a major role in health care. This study aims to assess pharmacists prospective and general health wellbeing during COVID-19 pandemic in Saudi Arabia. Methods: We conducted a cross sectional observational study using a quantitative survey-based methodology. Data was collected from May to July 2020. Results: We were able to enrol 381 pharmacists working in different practice settings as governmental hospitals, healthcare centers, private hospitals and community pharmacies. The acceptable knowledge level score is 13 (60%) that has been reached by about 37% of participants. Male and female had similar scores. Level of knowledge among regions was variable, southern region scored the least with a mean score of 12.89 ± 3.91 and eastern region scored the highest level with a mean score of 15.07 ± 2.86. There was a significant correlation between knowledge level, region of residency and level of experience. The maximum total awareness score was 7, the mean score was 5.18 ± 1.65. There was a statistically significant correlation between awareness level and the region of residency variable. The general health questions section included 9 questions. The minimum score was 9, the maximum was 36 and the mean score was 17.51 ± 7.34. The higher the score indicate the worsening of the general health. There is a strong correlation between gender, experience and the general health wellbeing. Men had better general health compared to women p<0.001 and participants with range of experience 6-10 years had a lower level of general health. Conclusion: COVID-19 still has a negative impact worldwide. Maintaining awareness and education is essential to keep the protective measures as possible. In addition, there is a need to address the impact of COVID-19 on pharmacist's mental health to act accordingly.

scholarly journals Carbon Cycle Uncertainty in REgional Carbon Cycle Assessment and Processes (RECCAP)

2012 ◽  
Vol 9 (8) ◽  
pp. 2889-2904 ◽  
Author(s):  
I. G. Enting ◽  
P. J. Rayner ◽  
P. Ciais
Keyword(s):  
Standard Deviation ◽  
Carbon Cycle ◽  
Probability Distributions ◽  
Location Parameter ◽  
Carbon Budgets ◽  
Space And Time ◽  
Full Form ◽  
The Mean ◽  
Almost All ◽  
The Impact

Abstract. Characterisation of estimates of regional carbon budgets and processes is inherently a statistical task. In full form this means that almost all quantities used or produced are realizations or instances of probability distributions. We usually compress the description of these distributions by using some kind of location parameter (e.g. the mean) and some measure of spread or uncertainty (e.g. the standard deviation). Characterising and calculating these uncertainties, and their structure in space and time, is as important as the location parameter, but uncertainties are both hard to calculate and hard to interpret. In this paper we describe the various classes of uncertainty that arise in a process like RECCAP and describe how they interact in formal estimation procedures. We also point out the impact these uncertainties will have on the various RECCAP synthesis activities.

scholarly journals Evidence from Urban Roads without Bicycle Lanes on the Impact of Bicycle Traffic on Passenger Car Travel Speeds

2020 ◽  
Vol 2674 (7) ◽  
pp. 87-98
Author(s):  
Jaclyn S. Schaefer ◽  
Miguel A. Figliozzi ◽  
Avinash Unnikrishnan
Keyword(s):  
Comparative Analysis ◽  
Confidence Intervals ◽  
Passenger Vehicle ◽  
Passenger Car ◽  
Lower Volume ◽  
The Mean ◽  
Motorized Vehicles ◽  
Car Travel ◽  
The Impact

A concern raised by some motorists in relation to the presence of bicycles on urban roads without bicycle lanes, discussed in part of the traffic literature, is that cyclists will slow down motorized vehicles and therefore create congestion. This research answers this question: do bicycles reduce passenger car travel speeds on urban roads without bicycle lanes? To answer this question, a detailed comparative analysis of the travel speeds of passenger car (class two vehicles) on lower volume urban roads without bicycle lanes is presented. Speed distributions, the mean, and the 50th and 85th percentile speeds for two scenarios were examined: (i) a passenger car that was preceded by a bicycle and (ii) a passenger car that was preceded by another passenger car. Peak hour traffic and 24-h traffic speeds were analyzed using t-tests and confidence intervals. Although a few statistically significant differences between scenarios (i) and (ii) were found, the actual speed differences were generally in the order of 1 mph or less. Therefore, differences in class two (motorized passenger) vehicle speeds with and without cyclists were found to be negligible from a practical perspective.

scholarly journals Probability Distribution Characteristics for Surface Air–Sea Turbulent Heat Fluxes over the Global Ocean

2012 ◽  
Vol 25 (1) ◽  
pp. 184-206 ◽  
Author(s):  
Sergey K. Gulev ◽  
Konstantin Belyaev
Keyword(s):  
Probability Density ◽  
Interannual Variability ◽  
Probability Distributions ◽  
Heat Fluxes ◽  
Western Boundary ◽  
Turbulent Heat ◽  
Boundary Current ◽  
Turbulent Heat Fluxes ◽  
The Mean ◽  
The Impact

Abstract To analyze the probability density distributions of surface turbulent heat fluxes, the authors apply the two-parametric modified Fisher–Tippett (MFT) distribution to the sensible and latent turbulent heat fluxes recomputed from 6-hourly NCEP–NCAR reanalysis state variables for the period from 1948 to 2008. They derived the mean climatology and seasonal cycle of the location and scale parameters of the MFT distribution. Analysis of the parameters of probability distributions identified the areas where similar surface turbulent fluxes are determined by the very different shape of probability density functions. Estimated extreme turbulent heat fluxes amount to 1500–2000 W m−2 (for the 99th percentile) and can exceed 2000 W m−2 for higher percentiles in the subpolar latitudes and western boundary current regions. Analysis of linear trends and interannual variability in the mean and extreme fluxes shows that the strongest trends in extreme fluxes (more than 15 W m−2 decade−1) in the western boundary current regions are associated with the changes in the shape of distribution. In many regions changes in extreme fluxes may be different from those for the mean fluxes at interannual and decadal time scales. The correlation between interannual variability of the mean and extreme fluxes is relatively low in the tropics, the Southern Ocean, and the Kuroshio Extension region. Analysis of probability distributions in turbulent fluxes has also been used in assessing the impact of sampling errors in the Voluntary Observing Ship (VOS)-based surface flux climatologies, allowed for the estimation of the impact of sampling in extreme fluxes. Although sampling does not have a visible systematic effect on mean fluxes, sampling uncertainties result in the underestimation of extreme flux values exceeding 100 W m−2 in poorly sampled regions.

On Effect of Model Parameters on Departure Process in a Production System with Failures

2014 ◽  
Vol 1036 ◽  
pp. 927-932 ◽  
Author(s):  
Wojciech M. Kempa ◽  
Iwona Paprocka ◽  
Cezary Grabowik ◽  
Krzysztof Kalinowski
Keyword(s):  
Probability Distributions ◽  
Distributed Processing ◽  
Fixed Time ◽  
Model Parameters ◽  
Exponential Distributions ◽  
Departure Process ◽  
System Of Integral Equations ◽  
Manufacturing Line ◽  
The Mean ◽  
The Impact

A queueing system of the M/M/1/N type with cyclic failure-free and repair times is used as a model of a single-machine manufacturing line. Jobs arrive according to a Poisson process and are being served with exponentially distributed processing time. Successive working (failure-free) and repair times have exponential distributions, too. Basing on a system of integral equations for double transforms of conditional probability distributions of the number of jobs completely processed before the fixed time (departure process), comprehensive numerical analysis of the impact of system parameters on the mean number of departures before the fixed epoch T>0 is carried out.

scholarly journals RECCAP uncertainty

2012 ◽  
Vol 9 (2) ◽  
pp. 1829-1868 ◽  
Author(s):  
I. G. Enting ◽  
P. J. Rayner ◽  
P. Ciais
Keyword(s):  
Standard Deviation ◽  
Probability Distributions ◽  
Location Parameter ◽  
Carbon Budgets ◽  
Space And Time ◽  
Estimation Procedures ◽  
Full Form ◽  
The Mean ◽  
Almost All ◽  
The Impact

Abstract. Characterisation of regional carbon budgets and processes (the overall task addressed in this series of articles) is inherently a statistical task. In full form this means that almost all quantities used or produced are realizations or instances of probability distributions. We usually compress the description of these distributions by using some kind of location parameter (e.g. the mean) and some measure of spread or uncertainty (e.g. the standard deviation). Characterising and calculating these uncertainties, and their structure in space and time, is as important as the location parameter but uncertainties are both harder to calculate and harder to interpret. In this paper we describe the various classes of uncertainty that arise in a process like RECCAP and describe how they interact in formal estimation procedures. We also point out the impact these uncertainties will have on the various RECCAP synthesis activities.

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