Wald Confidence Interval Research Articles

Using the standard Wald confidence interval for a population proportion hypothesis test is a common mistake

SummaryEmploying a Wald confidence interval to test hypotheses about population proportions could lead to an increase in Type I or Type II errors unless the hypothesized value, p0, is used in computing its standard error rather than the sample proportion.

Development of a site fidelity index based on population capture-recapture data.

BackgroundSite fidelity is considered as an animal’s tendency to return to a previously occupied place; this is a component of animal behaviour that allows us to understand movement patterns and aspects related to the animal’s life history. Although there are many site fidelity metrics, the lack of standardisation presents a considerable challenge in terms of comparability among studies.MethodsThis investigation focused on the theoretical development of a standardised composite site fidelity index and its statistical distribution in order to obtain reliable population-level site fidelity comparisons. The arithmetic and harmonic means were used as mathematical structures in order to create different indexes by combining the most commonly used indicators for site fidelity such as Occurrence, Permanence and Periodicity. The index performance was then evaluated in simulated populations and one real population of Commerson’s dolphins (Cephalorhynchus commersonii (Lacépède 1804)). In the first case, the indexes were evaluated based on how they were affected by different probability values such as the occurrence of the individual within the study area (φ) and capture probability (p). As a precision measure for the comparison of the indexes, the Wald confidence interval (CI) and the mean square error were applied. Given that there was no previous data concerning the distribution parameters of this population, bootstrap CIs were applied for the study case.ResultsEight alternative indexes were developed. The indexes with an arithmetic mean structure, in general, had a consistently inferior performance than those with a harmonic mean structure. The index IH4, in particular, achieved the best results in all of the scenarios and in the study case. Additionally, this index presented a normal distribution. As such, it was proposed as a standardised measure for site fidelity (Standardised Site Fidelity Index—SSFI).DiscussionThe SSFI is the first standardised metric that quantifies site fidelity at a populational level. It is an estimator that varies between zero and one and works in situations where detection is not perfect and effort can be constant or not. Moreover, it has an associated CI that allows users to make comparisons.

Effective plasma alfaxalone concentration to produce immobility in male neutered cats

ObjectiveTo determine the effective plasma alfaxalone concentration for the production of immobility in cats. Study designProspective up-and-down study. AnimalsSixteen 1–2 year old male castrated research cats. MethodsCats were instrumented with catheters in a jugular and a medial saphenous vein. Alfaxalone was administered via the medial saphenous catheter, using a target-controlled infusion system. The infusion lasted for approximately 32 minutes. A noxious stimulus (tail clamp) was applied 30 minutes after starting the alfaxalone infusion, until the cat moved or 60 seconds had elapsed, whichever occurred first. The target alfaxalone concentration was set at 5 mg L−1 in the first cat and increased or decreased by 1 mg L−1 in subsequent cats, if the previous cat had moved or not moved in response to stimulation, respectively. This was continued until six independent crossovers (different responses in pairs of subsequent cats) had been observed. Blood samples were collected before alfaxalone administration, and 15 and 31 minutes after starting the administration, for the determination of plasma alfaxalone concentration using liquid chromatography/tandem mass spectrometry. The alfaxalone concentration yielding a probability of immobility in 50% (EC50), 95% (EC95) and 99% (EC99) of the population, and their respective 95% Wald confidence intervals were calculated. ResultsThe EC50, EC95 and EC99 for alfaxalone-induced immobility were 3.7 (2.4–4.9), 6.2 (4.7–) and 7.6 (5.5–) mg L−1, respectively. Conclusions and clinical relevanceThe effective plasma alfaxalone concentration for immobility in cats was determined. This value will help in the design of pharmacokinetic-based dosing regimens.

Abstract TP291: Frequency of Neurological Evaluation and Neuroimaging in Patients With Infective Endocarditis

Introduction: Stroke is a frequent complication of infective endocarditis, but there are few data and guidelines to inform appropriate neurological evaluation and imaging in this setting. We sought to determine how often patients with endocarditis undergo neuroimaging and evaluation by a neurologist. Methods: Using claims between 2009-2015 from a 5% sample of Medicare beneficiaries, we identified all patients ≥66 years of age who were hospitalized with infective endocarditis, as defined by previously validated ICD-9-CM codes. Using CPT codes and Medicare provider specialty codes from claims submitted during the hospitalization, we ascertained our outcomes of brain imaging (CT or MRI), intracranial vessel imaging (CTA, MRA, or catheter angiography), and evaluation by a neurologist. We first assessed these outcomes in all patients hospitalized with infective endocarditis, and then in the subset of patients who had a concurrent diagnosis of stroke. Stroke was ascertained using a validated ICD-9-CM code algorithm and defined as the composite of ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. We used descriptive statistics with Wald confidence intervals (CI) to report crude rates. Results: Among 3,200 patients with infective endocarditis, brain imaging was performed in 34.5% (95% CI, 32.8-36.1%) of patients, intracranial vessel imaging in 4.7% (95% CI, 4.0-5.5%), and evaluation by a neurologist in 18.1% (95% CI, 16.8-19.5%). In this overall cohort, 343 (10.7%) patients had a concurrent diagnosis of stroke, 292 (85.1%) of which were ischemic. Among the 343 patients with both endocarditis and stroke, brain imaging was performed in 89.5% (95% CI, 86.3-92.7%) of cases, intracranial vessel imaging in 35.0% (95% CI, 30.0-40.0%), and neurologist evaluation in 74.6% (95% CI, 69.7-79.2%). Conclusions: In a nationally representative cohort of Medicare beneficiaries, we found that approximately one-third of patients with infective endocarditis underwent brain imaging and few were evaluated by a neurologist or received intracranial vessel imaging. Most patients with endocarditis complicated by stroke underwent head imaging and were seen by a neurologist, but a minority received intracranial vessel imaging.

Safety and long-term effectiveness of paroxysmal atrial fibrillation ablation with a contact force-sensing catheter: real-world experience from a prospective, multicentre observational cohort registry.

Real-time contact force (CF)-sensing radiofrequency ablation catheter for treatment of paroxysmal atrial fibrillation (PAF) allows optimization of electrode-tissue contact, which correlates with long-term success. This prospective, multicentre observational registry assessed the real-world clinical effectiveness of a CF-sensing catheter for ablation of drug-refractory PAF. Patients were followed-up at 3, 6, and 12 months after ablation. Outcome measures included isolation of targeted pulmonary veins (PVs) confirmed by entrance block (acute success), patient-reported freedom from symptomatic atrial fibrillation (AF) at 12 months (long-term effectiveness), Atrial Fibrillation Effect on Quality-of-life scores at 6 and 12 months, and incidence of predefined procedural complications. The registry enrolled 261 PAF patients (mean age 58.8 ± 11.3 years; 70.7% men; 91.7% Caucasian). Acute PV isolation was reported in 98.8% of patients [95% confidence interval (CI): 96.4-99.7%], and 12-month success for freedom from symptomatic AF was 75.7% (95% CI: 69.7-80.7%). Average CF for the evaluable cohort was 16.4 ± 3.9 g. There was a significant correlation between long-term effectiveness and stability of CF use [percentage of time CF was within investigator-selected working range; odds ratio (95% Wald CI), 1.0 (1.00-1.1); P = 0.030]. Average CF did not correlate with 12-month success. Clinically meaningful quality of life (QoL) improvements were observed at 6 and 12 months. Primary adverse events occurred in 2.7% patients. This observational registry showed that PAF ablation with a CF-sensing catheter had high acute success rates, favourable 12-month outcomes, and a good safety profile. Patients' QoL improved significantly. Long-term effectiveness significantly correlated with stable CF with adequate catheter-tissue contact (NCT01677052).

Non-Parametric Evidence of Second-Leg Home Advantage in European Football

SummaryIn international football (soccer), two-legged knockout ties, with each team playing at home in one leg and the final outcome decided on aggregate, are common. Many players, managers and followers seem to believe in ‘second-leg home advantage’, i.e. that it is beneficial to play at home on the second leg. A more complex effect than the well-documented usual home advantage, it is more difficult to identify, and previous statistical studies have not proved conclusive about its actuality. As opposed to previous research, the paper addresses the question from a purely non-parametric perspective, which is not based on any particular model specification which could orientate the analysis in one or the other direction. Along the way, the paper reviews the well-known shortcomings of the Wald confidence interval for a proportion, suggests new non-parametric confidence intervals for conditional probability functions, revisits the problems of bias and bandwidth selection when building confidence intervals in non-parametric regression and provides a novel bootstrap-based solution to them. Finally, the new intervals are used when analysing game outcome data for the UEFA (Union of European Football Associations) Champions and Europa Leagues from 2009–2010 to 2014–2015. A slight second-leg home advantage is evidenced.

An Interval Estimation Method of Patent Keyword Data for Sustainable Technology Forecasting

Technology forecasting (TF) is forecasting the future state of a technology. It is exciting to know the future of technologies, because technology changes the way we live and enhances the quality of our lives. In particular, TF is an important area in the management of technology (MOT) for R&D strategy and new product development. Consequently, there are many studies on TF. Patent analysis is one method of TF because patents contain substantial information regarding developed technology. The conventional methods of patent analysis are based on quantitative approaches such as statistics and machine learning. The most traditional TF methods based on patent analysis have a common problem. It is the sparsity of patent keyword data structured from collected patent documents. After preprocessing with text mining techniques, most frequencies of technological keywords in patent data have values of zero. This problem creates a disadvantage for the performance of TF, and we have trouble analyzing patent keyword data. To solve this problem, we propose an interval estimation method (IEM). Using an adjusted Wald confidence interval called the Agresti–Coull confidence interval, we construct our IEM for efficient TF. In addition, we apply the proposed method to forecast the technology of an innovative company. To show how our work can be applied in the real domain, we conduct a case study using Apple technology.

Presumptive Treatment of Chlamydia and Gonorrhea Infections in a Canadian Ambulatory Emergency Department Setting

Objectives Presumptive antibiotic treatment may be given for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) infections before a laboratory diagnosis is established, but overtreatment can increase resistance rates. We sought to determine the presumptive treatment prevalence in our emergency department (ED) setting, as well as the number of overtreated and undertreated patients. Methods We performed a retrospective cohort study of all patients tested for CT/GC in an urban academic ED during a 6-month period in 2015. Presumptive treatment prevalence, overtreatment and undertreatment proportions, and CT- and GC-positive test proportions were calculated with 95% Wald confidence interval (CI) and compared across age and sex. Results Of 209 included cases (male n = 3, female n = 206), 27 (13%; CI, 8%–18%) received presumptive treatment for CT and 19 (9%; CI, 5%–14%) for GC. Seven cases (3%; CI, 1%–6%) were positive for CT and 0 for GC. Of the 7 CT-positive cases, 2 (29%) received presumptive treatment in the ED, and 5 (71%) were treated after the positive test results were obtained. There was no loss to follow-up. Mean delay to treatment was 10 days, including a mean of 3 days for laboratory analysis. Overtreatment and undertreatment proportions were 93% (CI, 83%–100%) and 3% (CI, 0%–5%) for CT and 100% and 0% for GC, respectively. Positive test result, presumptive treatment, overtreatment, and undertreatment were not associated with age or sex. Conclusions Given the low CT/GC incidence and good follow-up, at our institution, it would be reasonable to wait for a laboratory diagnosis rather than give presumptive treatment.

372 Derivation of a Clinical Decision Instrument to Identify Adults in a Community Setting With Mild Traumatic Intracranial Hemorrhage at Low Risk for Requiring Critical Care Intervention

Adults presenting to the ED with mild traumatic intracranial hemorrhage (tICH) are commonly admitted to the intensive care unit (ICU), although critical care interventions are often unnecessary. In prior research, we found that a clinical decision instrument (CDI) derived at an academic Level I trauma center to identify adults at low risk for critical care interventions performed poorly in a community setting, likely because of substantial differences in patient case-mix. We sought to derive a more generalizable CDI among patients of a large community-based integrated health care delivery system. This retrospective cohort study included non-anticoagulated adults (≥18 years of age) with mild tICH, defined as GCS score ≥13, across 21 community EDs from 01/2012 to 12/2013. No study facility carried a Level I trauma center designation, and only one carried a Level II designation. The primary outcome of at least one critical care intervention within 48 hours of ED arrival included intubation, neurosurgical intervention, vasopressor or inotrope use, invasive monitoring, or cardiopulmonary resuscitation. Using logistic regression with single independent variables, we identified potential predictors of the outcome, developed a 6-variable predictive logistic regression model, and created a simplified CDI to identify low-risk patients based on predicted probabilities from the model. We examined the prevalence of patients designated low-risk by both CDIs and compared performance metrics. We calculated sensitivity and specificity with Clopper-Pearson, positive and negative predictive values with standard logit, and c-statistics with Wald confidence interval (CI) estimates. Our cohort included 929 patients with mean age of 73.3 (SD 17.0) years; 50% were female, and 82% were injured by a ground-level fall. Of these, 110 (11.8%) received at least one critical care intervention, 100 of whom received a neurosurgical operation, mannitol or hypertonic saline. Patients identified as low risk had none of the following: time from trauma to ED >7 days, ED admitting GCS <15, lowest ED systolic blood pressure >140 mmHg, CT evidence of skull fracture, mass effect, or midline shift >5 mm. The new CDI designated nearly three times as many patients as low-risk than the academic-based CDI with similar sensitivity and significantly higher specificity (see Table). We derived a CDI to identify patients with mild tICH at low risk for requiring ICU-level care in this community setting. The community-based instrument was equally sensitive as its academic counterpart, but outperformed it with a greater specificity and positive predictive value. This lower rate of false positives may increase its ultimate clinical utility. Continued model development may further improve specificity, and a prospective validation study will be needed prior to clinical implementation.

Staying in service with posttraumatic headache: A retrospective cohort study of patient outcome.

To predict the probability of a military outcome (medical discharge/retirement) in patients with mild traumatic brain injury from a clinical analysis of predetermined patient and headache characteristics. This retrospective cohort study sampled all new patients referred for headache evaluation at the Brain Injury Clinic of the Womack Army Medical Center, Ft. Bragg, NC (August 2008-January 2010). Headache characteristics were extracted and analyzed. Multivariable binary logistic regressions were conducted to predict probability of medical discharge/retirement. Ninety-five soldiers (age 31.3 ± 7.4 years, male 93.7%) reported 166 headaches. The most common injury cited was a blast (53.7%). Patients with a continuous headache have almost 4 times the odds of a medically related discharge/retirement compared to patients without such a headache (continuous headache regression coefficient estimate: p < 0.042, odds ratio 3.98, 95% Wald confidence interval 1.05-15.07). Results suggest that, compared to service members who did not have a continuous headache, patients with headache histories with severe holocephalic pain who medicate to keep functioning had the highest probability of medical discharge/retirement. Certain headache characteristics may be predictive of military outcomes after mild traumatic brain injury, and we propose a profile that may be useful in that prediction. These data could be useful in future attempts to assess and treat patients with posttraumatic headache and to advise longer-term planning for return to duty or discharge.

Sex Differences In Head Injuries Among Collegiate Soccer Players

Some of the highest rates of head injuries and concussion among all contact/collision sports are observed in soccer; yet, the multifactorial determinants of head injuries among players remain relatively undefined. PURPOSE: To examine sex-differences in the rate and the severity (lost days of participation, resultant concussions) of head injuries among collegiate soccer players between 2004 and 2009, while controlling for several covariables previously linked to injury occurrence. METHODS: Data from the National Collegiate Athletic Association Injury Surveillance System (NCAA-ISS) were used to calculate injury incidence density (ID) per 1000 athletic exposures (AE). The rate ratio (RR), along with the 95% Wald confidence interval (CI), compared ID among female, relative to male soccer players. Multivariable logistic regression and multivariable negative binomial regression modeling then tested the relation between sex and head injury incidence and severity while controlling for contact, setting, and competition level. RESULTS: Between 2004 and 2009, the sex-specific rate of soccer-related head injuries was 0.87 per 1000 AEs in women and 0.71 per 1000 AEs in men (RR = 1.23, 95% CI = [1.08, 1.41]). The rate of head injuries due to player-to-player contact was comparable between women and men (RR=0.95, 95% CI=[0.81, 1.11]); however, the rate of injury due to contact with apparatus was nearly 2 ½ -fold higher (RR=2.46, 95% CI = [1.76, 3.44]) and the rate due to contact with a playing surface was over two-fold higher (RR=2.29, 95% CI = [1.34, 3.91]) in women than in men. We also observed a significant joint effect between sex and contact in our regression models, with a particularly notable antagonistic interaction observed while modeling head injuries. CONCLUSION: Among female players, head contact with a ball, a goal post, or the playing surface may be especially deleterious compared with head contact with another player.

Moving to business \u2013 changes in physical activity and sedentary behavior after multilevel intervention in small and medium-size workplaces

BackgroundRegular physical activity (PA) promotes and excessive sedentary behavior (SB) deteriorates health. Yet the Finnish working-aged population spends most of the day sitting. A 1-year Moving To Business (MTB) -intervention supported small and medium-size workplaces to combat sedentariness. This paper reports the changes in employees’ PA and SB from before MTB (baseline) to 1 year after baseline (follow-up).MethodsTwelve workplaces with a total of 396 employees participated. Each workplace nominated a team to promote PA and reduce SB at organizational, working unit and employee level. The teams were mentored regionally through meetings, workshop and tools. Changes in PA and SB were assessed with a questionnaire and an accelerometer. Wald Confidence Interval (Cl) for a difference of proportions with matched pairs was used in the questionnaire data (%-points with 95% CI) and linear mixed model in the accelerometer data (minutes and % of wear-time with 95% CI).ResultsThe mean age of the respondents to the questionnaire (N = 296; 75%) was 42.6 (SD 10.9), 64% were women, 95% had some education after high school, 74% worked in the day shift, 71% did sedentary work and 51% were overweight. The mean number of actions implemented in the workplaces was 6.8 and the multilevel approach was fully applied in 6 workplaces. Based on the questionnaire the time spent in SB decreased from baseline to follow-up 16% (95% CI −29 to −3) in total and 22% (−41 to −3) at work. The accelerometer showed daily increases of 33.7 min (15.3 to 52.1) and 6.8% (3.1 to 10.4) in total PA, 30.9 min (15.3 to 46.5) and 6.1% (2.9 to 9.2) in light PA and 673 (209 to 1139) more steps at work. Daily SB at work decreased 44.9 min (−68.0 to −21.8) and 7.6% (−11.9 to −3.2). Daily leisure PA declined 11.0 min (−24.9 to 2.9) and 3.2% (−6.2 to −0.2). Number of levels or actions had no effect on changes.ConclusionsEmployees’ PA increased and SB reduced at work during the intervention. At the same time leisure PA decreased slightly. Workplaces can achieve meaningful changes in employees’ PA and SB if assisted systematically. Controlled studies are needed to confirm the present findings.Trial registrationNCT01999205, registration date 11/01/2013.

A Classroom Approach to Illustrate Transformation and Bootstrap Confidence Interval Techniques Using the Poisson Distribution

The Poisson distribution is here used to illustrate transformation and bootstrap techniques in order to construct a confidence interval for a mean. A comparison is made between the derived intervals and the Wald and score confidence intervals. The discussion takes place in a classroom, where the teacher and the students have previously discussed and evaluated the Wald and score confidence intervals. While step by step interactively getting acquainted with new techniques, the students will learn about the effects of e.g. bias and asymmetry and ways of dealing with such phenomena. The primary purpose of this teacher-student communication is therefore not to find the best possible interval estimator for this particular case, but rather to provide a study displaying a teacher and her/his students interacting with each other in an efficient and rewarding way. The teacher has a strategy of encouraging the students to take initiatives. This is accomplished by providing the necessary background of the problem and some underlying theory after which the students are confronted with questions and problem solving. From this the learning process starts. The teacher has to be flexible according to how the students react. The students are supposed to have studied mathematical statistics for at least two semesters.

Survey of vaccination knowledge and acceptance among adults admitted to an urban emergency department

BackgroundAdult vaccination rates in the United States have fallen below national target levels and may be exacerbated by lack of access to a primary care physician. We assessed patient knowledge of and attitudes towards vaccines in an urban emergency department population and analyzed the feasibility of using this setting as a vaccine delivery site from a patient perspective. MethodsIn-person interviewers administered surveys to 250 adult patients presenting to the Detroit Receiving Hospital emergency department in Detroit, Michigan. Respondents were asked about vaccination status, preferences, and willingness to accept vaccination reminders via text messaging. Odds ratios and 95% Wald confidence intervals assessing differences between vaccinated and non-vaccinated individuals were generated with univariate logistic regression. ResultsVaccinated adults were more likely to have a primary care provider than non-vaccinated adults (OR 1.94, 95% CI: 1.09–3.45). Non-vaccinated adults were significantly more likely to have unvaccinated adult relatives (OR8.64, 95% CI: 4.10–18.22). Nearly all respondents used a cell phone, and 75.8% of unvaccinated adults were willing to receive text messages reminders about vaccines. ConclusionsAlthough less likely to have a primary care access point than vaccinated participants, non-vaccinated respondents reported interest in receiving vaccinations. Emergency departments could serve as vaccination hubs for patients and unvaccinated accompanying family members. Text message reminders offer a potential source of additional vaccine prompts and education.

Standardized Parameters in Misspecified Structural Equation Models: Empirical Performance in Point Estimates, Standard Errors, and Confidence Intervals

In practice, models always have misfit, and it is not well known in what situations methods that provide point estimates, standard errors (SEs), or confidence intervals (CIs) of standardized structural equation modeling (SEM) parameters are trustworthy. In this article we carried out simulations to evaluate the empirical performance of currently available methods. We studied maximum likelihood point estimates, as well as SE estimators based on the delta method, nonparametric bootstrap (NP-B), and semiparametric bootstrap (SP-B). For CIs we studied Wald CI based on delta, and percentile and BCa intervals based on NP-B and SP-B. We conducted simulation studies using both confirmatory factor analysis and SEM models. Depending on (a) whether point estimate, SE, or CI is of interest; (b) amount of model misfit; (c) sample size; and (d) model complexity, different methods can be the one that renders best performance. Based on the simulation results, we discuss how to choose proper methods in practice.

Effects of a single intravenous bolus of fentanyl on the minimum anesthetic concentration of isoflurane in chickens (Gallus gallus domesticus)

ObjectiveTo assess the temporal effects of a single fentanyl intravenous (IV) bolus on the minimum anesthetic concentration (MAC) of isoflurane in chickens and to evaluate the effects of this combination on heart rate (HR) and rhythm, systemic arterial pressures (sAP) and ventilation. Study designProspective experimental trial. AnimalsSeventeen adult chickens weighing 1.8±0.2 kg. MethodsIndividual isoflurane MAC for 17 chickens was previously determined using the bracketing method. Chickens were anesthetized with isoflurane to evaluate the effects of a single IV fentanyl bolus (10 or 30 μg kg−1) on isoflurane MAC over time using the up-and-down method. Ventilation was controlled. The isoflurane MAC reduction was estimated by logistic regression at 5 and 15 minutes after fentanyl administration. In the second phase, seven chickens were anesthetized with isoflurane, and fentanyl was administered (30 μg kg−1) IV over 1 minute during spontaneous ventilation and HR and rhythm, sAP and ventilation variables were measured. ResultsAt 5 minutes after IV administration of fentanyl (10 or 30 μg kg−1), isoflurane MAC was significantly reduced by 17.6% (6.1–29.1%) [logistic regression estimate (95% Wald confidence interval)] and 42.6% (13.3–71.9%), respectively. Isoflurane MAC reduction at 15 minutes after IV administration of fentanyl (10 or 30 μg kg−1) was 6.2% (−0.6 to 12.9%) and 13.2% (−0.9 to 27.3%), respectively; however, this reduction was not significant. No clinically significant cardiopulmonary changes or arrhythmias were detected after the administration of fentanyl (30 μg kg−1). Conclusions and clinical relevanceAdministration of a single fentanyl bolus induced a dose-dependent and short-lasting reduction in isoflurane MAC. The higher dose induced no significant cardiopulmonary depression in isoflurane-anesthetized chickens during spontaneous ventilation. In chickens anesthetized with isoflurane, the clinical usefulness of a single fentanyl bolus is limited by its short duration of effect.

Comparing Parameter Estimates Obtained by Simulation Study and Real Life Data from the Two-Parameter Gamma Model

The aim of this study was to employ Maximum Likelihood (MLE) jointly with a numerical Method (Newton Raphson method) to obtain parameter estimates from the two-parameter Gamma model. The profile likelihood of the two-parameter Gamma model was also put into consideration. The methods were demonstrated using simulation studies and real life data considering data sets generated by R statistical software for different sample sizes. Standard errors were computed and 5 % Wald-confidence interval was constructed for the estimates of the model. The result of the study shows that Maximum Likelihood Estimation (MLE) jointly with Newton Raphson method was more efficient for estimating parameters of the Gamma model in simulation study than real life data. The study recommends that parameter estimates from the two-parameter Gamma model should be obtained by employing Maximum Likelihood Estimation jointly with Newton Raphson Method.

Use of Oral Cholera Vaccine and Knowledge, Attitudes, and Practices Regarding Safe Water, Sanitation and Hygiene in a Long-Standing Refugee Camp, Thailand, 2012-2014.

Oral cholera vaccines (OCVs) are relatively new public health interventions, and limited data exist on the potential impact of OCV use on traditional cholera prevention and control measures—safe water, sanitation and hygiene (WaSH). To assess OCV acceptability and knowledge, attitudes, and practices (KAPs) regarding cholera and WaSH, we conducted cross-sectional surveys, 1 month before (baseline) and 3 and 12 months after (first and second follow-up) a preemptive OCV campaign in Maela, a long-standing refugee camp on the Thailand-Burma border. We randomly selected households for the surveys, and administered questionnaires to female heads of households. In total, 271 (77%), 187 (81%), and 199 (85%) households were included in the baseline, first and second follow-up surveys, respectively. Anticipated OCV acceptability was 97% at baseline, and 91% and 85% of household members were reported to have received 1 and 2 OCV doses at first follow-up. Compared with baseline, statistically significant differences (95% Wald confidence interval not overlapping zero) were noted at first and second follow-up among the proportions of respondents who correctly identified two or more means of cholera prevention (62% versus 78% and 80%), reported boiling or treating drinking water (19% versus 44% and 69%), and washing hands with soap (66% versus 77% and 85%); a significant difference was also observed in the proportion of households with soap available at handwashing areas (84% versus 90% and 95%), consistent with reported behaviors. No significant difference was noted in the proportion of households testing positive for Escherichia coli in stored household drinking water at second follow-up (39% versus 49% and 34%). Overall, we observed some positive, and no negative changes in cholera- and WaSH-related KAPs after an OCV campaign in Maela refugee camp. OCV campaigns may provide opportunities to reinforce beneficial WaSH-related KAPs for comprehensive cholera prevention and control.

Model-robust inference for continuous threshold regression models.

We study threshold regression models that allow the relationship between the outcome and a covariate of interest to change across a threshold value in the covariate. In particular, we focus on continuous threshold models, which experience no jump at the threshold. Continuous threshold regression functions can provide a useful summary of the association between outcome and the covariate of interest, because they offer a balance between flexibility and simplicity. Motivated by collaborative works in studying immune response biomarkers of transmission of infectious diseases, we study estimation of continuous threshold models in this article with particular attention to inference under model misspecification. We derive the limiting distribution of the maximum likelihood estimator, and propose both Wald and test-inversion confidence intervals. We evaluate finite sample performance of our methods, compare them with bootstrap confidence intervals, and provide guidelines for practitioners to choose the most appropriate method in real data analysis. We illustrate the application of our methods with examples from the HIV-1 immune correlates studies.

Matching pseudocounts for interval estimation of binomial and Poisson parameters

ABSTRACTFor interval estimation of a binomial proportion and a Poisson mean, matching pseudocounts are derived, which give the one-sided Wald confidence intervals with second-order accuracy. The confidence intervals remove the bias of coverage probabilities given by the score confidence intervals. Partial poor behavior of the confidence intervals by the matching pseudocounts is corrected by hybrid methods using the score confidence interval depending on sample values.