Interval Procedure Research Articles

The Run Sum Hotelling's χ2 Control Chart with Variable Sampling Intervals

Control charts are widely used for process monitoring and quality control in manufacturing industries. Implementing variable sampling interval (VSI) control schemes on control charts rather than traditional fixed sampling interval procedure can significantly improve the control chart's efficiency. In this paper, the VSI run sum (RS) Hotelling's χ2 chart is proposed. The optimal scores and parameters of the proposed chart are determined using an optimization technique to minimize the following: (i) out‐of‐control average time to signal (ATS); (ii) adjusted ATS (AATS), when the exact shift size can be specified; (iii) expected ATS; or (iv) expected AATS, when the exact shift size cannot be specified. The Markov chain method is used to evaluate the zero‐state ATS and expected ATS, and steady‐state AATS and expected AATS of the proposed chart. The results show that the VSI RS Hotelling's χ2 chart significantly outperforms the standard RS Hotelling's χ2 chart and the former also performs well compared with other competing charts. By adding more scoring regions, the efficiency of the VSI RS Hotelling's χ2 chart can be further enhanced. An illustrative example using data from a manufacturing process is presented to demonstrate the application of the VSI RS Hotelling's χ2 chart. The application of the proposed chart in a quality improvement program can be extended to management and service industries. Copyright © 2016 John Wiley & Sons, Ltd.

Unified Framework for Construction Project Integration

AbstractMoving the construction industry towards a more-integrated approach to project delivery could improve its overall performance. The aim of this paper is to develop a unified framework for project integration by identifying the critical success attribute and different levels of attribute importance, and by determining if there are major differences among the perceptions of survey respondents depending on their industry role. The survey sample (N=264) was composed of industry practitioners in the United States. The framework was developed using the Thurstone Scaling Method of Successive Interval Procedure; In addition, this method was complemented and validated using correlation analysis, cluster analysis, and analysis of variance (ANOVA). According to the perceptions of respondents, 19 of the 45 attributes under study were identified as critical for successfully achieving project integration. Four other categories of importance were identified. There were minor differences found between the percepti...

Interval laparoscopic abdominal cerclage for recurrent pregnancy loss

Abdominal cerclages are necessary when the standard trans-vaginal cerclages fail or anatomical abnormalities preclude the vaginal placement. In 1965, Benson and Durfee described an abdominal approach to cerclage, a procedure that was applied to congenitally short or surgically amputated cervices. Thirty-eight women with history of either recurrent mid-trimester pregnancy losses, short cervix or failed vaginal cerclage had trans-abdominal cerclage, of which 30 were done laparoscopically. A 5-mm non-absorbable needled polyester fibre tape (Mersilene) suture was placed laparoscopically at the level of the internal os as an interval procedure. All the procedures were successful. All women were discharged on post-operative day 2 and none of them required blood transfusions. There were no intraoperative or post-operative complications. Subsequently, 15 patients conceived and the foetal survival rate recorded was as high as 85.71%. Some patients manifest severe cervical injures, and others have apparent congenital absence of the cervix, rendering Shirodkar or McDonald cerclage technically difficult or impossible. The main interest of this technique is to avoid a laparotomy; thus, reducing the morbidities of a laparotomy and also the recovery time post-surgery.

Gastrointestinal perforation following blunt trauma abdomen: a study of 78 cases

Background: Blunt trauma to the abdomen leading to bowel injury is one of the major causes of death in the society. The most important problem associated with gastrointestinal perforation following blunt abdominal trauma is that they frequently remain undetected or are diagnosed too late despite advances in medical imaging. Objective: To evaluate gastrointestinal perforation following blunt abdominal trauma, their anatomical distribution, diagnosis, management, and outcome. Materials and Methods: The study was a prospective observational study conducted at the Department of General Surgery, SMS Medical College and Hospital, Jaipur, from April 2012 to October 2013 on 78 patients undergoing surgery for gastrointestinal perforation following blunt abdominal trauma. The study variables included sociodemographic data, radiological findings, perforation-surgery interval, intraoperative findings, and surgical procedure performed. Postoperative outcomes in terms of recovery, postoperative complications, and mortality were studied. Results: Of 78 patients, 76 were male and only 2 were female subjects. The incidence was more in the young age group (maximum in 21–30 years age group) with road traffic accident being the most common causative factor. Free gas under diaphragm in chest X-ray was found in 51 (65.4%) patients, while remaining of them was diagnosed by USG abdomen (20 patients) and in CT abdomen (7 patients). Jejunum was the most common site of perforation followed by ileum. Among the surgical procedures, simple closure with peritoneal lavage was the most commonly performed surgery. Postoperative complications were seen in 38 (48.7%) patients, with chest infection being the most common. Ten (12.8%) patients died in the postoperative period with a higher mortality rate in patients with delayed admission in hospital and increasing age (> 50 years). Conclusion: Posttraumatic gastrointestinal perforation most commonly involves the small intestine and can usually be managed by simple closure. Early surgery is associated with a good recovery. Risk of mortality increases with age > 50 years and delay in admission in hospital.

Laparoscopic Cerclage as a Treatment Option for Cervical Insufficiency.

Background: The traditional surgical treatment for cervical insufficiency is vaginal placement of a cervical cerclage. However, in a small number of cases a vaginal approach is not possible. A transabdominal approach can become an option for these patients. Laparoscopic cervical cerclage is associated with good pregnancy outcomes but comes at the cost of a higher risk of serious surgical complications. The aim of the present study was to evaluate intraoperative and long-term pregnancy outcomes after laparoscopic cervical cerclage, performed either as an interval procedure or during early pregnancy, using a new device with a blunt grasper and a flexible tip. Methods: All women who underwent laparoscopic cervical cerclage for cervical insufficiency in our institution using the Goldfinger® device (Ethicon Endo Surgery, Somerville, NJ, USA) between January 2008 and March 2014 were included in the study. Data were collected from the patients' medical records and included complications during and after the above-described procedure. Results: Eighteen women were included in the study. Of these, six were pregnant at the time of laparoscopic cervical cerclage. Mean duration of surgery was 55 ± 10 minutes. No serious intraoperative or postoperative complications occurred. All patients were discharged at 2.6 ± 0.9 days after surgery. One pregnancy ended in a miscarriage at 12 weeks of gestation. All other pregnancies ended at term (> 37 weeks of gestation) with good perinatal and maternal outcomes. Summary: Performing a laparoscopic cervical cerclage using a blunt grasper device with a flexible tip does not increase intraoperative complications, particularly in early pregnancy. We believe that use of this device, which is characterized by increased maneuverability, could be an important option to avoid intraoperative complications if surgical access is limited due to the anatomical situation. However, because of the small sample size, further studies are needed to confirm our findings.

Using Invalid Instruments on Purpose: Focused Moment Selection and Averaging for GMM, Second Version

Infinite samples, the use of a slightly endogenous but highly relevant instrument can reduce mean-squared error (MSE). Building on this observation, I propose a moment selection criterion for GMM in which moment conditions are chosen based on the MSE of their associated estimators rather than their validity: the focused moment selection criterion (FMSC). I then show how the framework used to derive the FMSC can address the problem of inference post-moment selection. Treating post-selection estimators as a special case of moment-averaging, in which estimators based on different moment sets are given data-dependent weights, I propose a simulation-based procedure to construct valid confidence intervals for a variety of formal and informal moment-selection and averaging procedures. Both the FMSC and confidence interval procedure perform well in simulations. I conclude with an empirical example examining the effect of instrument selection on the estimated relationship between malaria transmission and income.

Nonpalpable intrauterine device threads: Is it a cause for worry?

BackgroundIntrauterine contraceptive device is a popular and effective method of contraception. It can be inserted either as an interval procedure or after abortion or delivery. Threads are attached to the vertical limb so that the user can find out the location of the device. Sometimes the threads are not palpable by the user; this study was conducted to find out the reasons for inability to palpate the threads. Methods and resultsThe retrospective study was conducted over a period of eight years; 110 female patients who complained of inability to feel the threads were included in the study. In most of the cases the device was in the right place. In four cases the device could not be felt on uterine sounding; this could have been due to subendometrial placement of the device. There was no case of perforation by the device. ConclusionInability to feel the threads is a common complaint by the patients who are using intrauterine contraceptive device. In most of the cases the device was in correct position and could be localized by clinical examination. Ultrasonography can help in localization of the device; if used at the time of insertion it can confirm proper insertion and location of the device. This will reassure the client and the health care providers.

Evaluating the Impact of Guessing and Its Interactions With Other Test Characteristics on Confidence Interval Procedures for Coefficient Alpha.

The effect of guessing on the point estimate of coefficient alpha has been studied in the literature, but the impact of guessing and its interactions with other test characteristics on the interval estimators for coefficient alpha has not been fully investigated. This study examined the impact of guessing and its interactions with other test characteristics on four confidence interval (CI) procedures for coefficient alpha in terms of coverage rate (CR), length, and the degree of asymmetry of CI estimates. In addition, interval estimates of coefficient alpha when data follow the essentially tau-equivalent condition were investigated as a supplement to the case of dichotomous data with examinee guessing. For dichotomous data with guessing, the results did not reveal salient negative effects of guessing and its interactions with other test characteristics (sample size, test length, coefficient alpha levels) on CR and the degree of asymmetry, but the effect of guessing was salient as a main effect and an interaction effect with sample size on the length of the CI estimates, making longer CI estimates as guessing increases, especially when combined with a small sample size. Other important effects (e.g., CI procedures on CR) are also discussed.

Failure of First-Line Antibiotics in Nonoperative Management of Appendiceal Mass, toward a Second-Line Instead of Surgery?

Background Conservative approach for complicated appendicitis has been gradually adopted in children to decrease postoperative morbidity. The first aim of this study was to assess the efficacy of a second-line antibiotics enlarged on Pseudomonas aeruginosa and Enterococcus in case of poor clinical outcome after initial conservative approach for appendiceal mass and abscess. The second aim of this study was to identify predictive factors of failure of first-line antibiotics. Methods We performed a prospective review of all the cases of appendiceal mass or abscess managed at our institution between November 2007 and September 2011 after implementation of a conservative protocol including a second-line antibiotics in case of poor initial clinical outcome. Results A total of 64 consecutive patients were included. We observed a success in 46 patients after the first-line antibiotics and in 14 of the remaining patients after the second-line. The only predictive factor of failure of the first-line antibiotics was a shorter duration of symptoms before admission (p = 0.02). Laparoscopic appendectomy was performed in all the cases (emergency or interval procedure) with six postoperative complications and two conversions to open surgery. Conclusions A gradual adapted antibiotherapy in nonoperative management of appendiceal abscess and mass is effective. We found no relevant predictive factor of failure of the first-line antibiotics.

Zero- vs. one-dimensional, parametric vs. non-parametric, and confidence interval vs. hypothesis testing procedures in one-dimensional biomechanical trajectory analysis

Biomechanical processes are often manifested as one-dimensional (1D) trajectories. It has been shown that 1D confidence intervals (CIs) are biased when based on 0D statistical procedures, and the non-parametric 1D bootstrap CI has emerged in the Biomechanics literature as a viable solution. The primary purpose of this paper was to clarify that, for 1D biomechanics datasets, the distinction between 0D and 1D methods is much more important than the distinction between parametric and non-parametric procedures. A secondary purpose was to demonstrate that a parametric equivalent to the 1D bootstrap exists in the form of a random field theory (RFT) correction for multiple comparisons. To emphasize these points we analyzed six datasets consisting of force and kinematic trajectories in one-sample, paired, two-sample and regression designs. Results showed, first, that the 1D bootstrap and other 1D non-parametric CIs were qualitatively identical to RFT CIs, and all were very different from 0D CIs. Second, 1D parametric and 1D non-parametric hypothesis testing results were qualitatively identical for all six datasets. Last, we highlight the limitations of 1D CIs by demonstrating that they are complex, design-dependent, and thus non-generalizable. These results suggest that (i) analyses of 1D data based on 0D models of randomness are generally biased unless one explicitly identifies 0D variables before the experiment, and (ii) parametric and non-parametric 1D hypothesis testing provide an unambiguous framework for analysis when one׳s hypothesis explicitly or implicitly pertains to whole 1D trajectories.

A Stepwise Confidence Interval Procedure Under Unknown Variances Based on an Asymmetric Loss Function for Toxicological Evaluation

SummaryOne of the most important issues in toxicity studies is the identification of the equivalence of treatments with a placebo. Because it is unacceptable to declare non‐equivalent treatments to be equivalent, it is important to adopt a reliable statistical method to properly control the family‐wise error rate (FWER). In dealing with this issue, it is important to keep in mind that overestimating toxicity equivalence is a more serious error than underestimating toxicity equivalence. Consequently asymmetric loss functions are more appropriate than symmetric loss functions. Recently Tao, Tang & Shi (2010) developed a new procedure based on an asymmetric loss function. However, their procedure is somewhat unsatisfactory because it assumes that the variances of various dose levels are known. This assumption is restrictive for some applications. In this study we propose an improved approach based on asymmetric confidence intervals without the restrictive assumption of known variances. The asymmetry guarantees reliability in the sense that the FWER is well controlled. Although our procedure is developed assuming that the variances of various dose levels are unknown but equal, simulation studies show that our procedure still performs quite well when the variances are unequal.

Uncertainties in dating constrain model choice for inferring extinction time from fossil records

Accurate estimates of the timing of extinctions (θ) are critical for understanding the causes of major die-off events and for identifying evolutionary or environmental transitions. Yet many studies have demonstrated that sampling biases and underlying statistical assumptions affect the accuracy of model-based estimates of extinction times (θˆ), and the added uncertainty contributed by inherent (laboratory) dating errors has largely been neglected. Here we provide a general guide (model-selection key) for choosing from among eight alternative ‘frequentist sampling’ (i.e., non-Bayesian) methods, differentiated by their treatment of both the probability of record occurrence and uncertainties in record dates, the most appropriate for a given record. We first provide a methodological framework to characterize time series of dated records as a function of the number of records, the size of the interval between successive records, and laboratory dating errors. Using both simulated data and dated Australian megafauna remains, we then assess how the characteristic of a dataset's time series dictates model performance and the probability of misclassification (false extant vs. false extinct). Among the four classic frequentist methods providing highest model performance, Marshall's (1997) and McCarthy's (1998) methods have the highest model precision. However, high model performance did not prevent misclassification errors, such that the Gaussian-resampled inverse-weighted McInerny (GRIWM) approach is the only method providing both high model accuracy and no misclassification issues, because of its unique down-weighting interval procedure and its ability to account for uncertainties in record dates. Applying the guideline to three time series of extinct Australian species, we recommend using Marshall's, McCarthy's and/or GRIWM methods to infer θ of both Thylacinus sp. and Genyornis sp., because each dataset is characterized by many sightings and a low variance of the interval between records, whereas McInerny's method better suits Diprotodon sp. due to an even lower interval variance.

Fibroepithelial Polyps of the Vagina in Pregnancy.

A 25-year-old primigravida mother at 36 weeks pregnancy presented with mass descending per vaginum for last one month. In the antenatal history she had regular antenatal visits without any pregnancy complication. General and systemic examination revealed no abnormality. On local examination of external genitalia, there was a large pedunculated polyp [Table/Fig-1] of the vagina which measured 8 x 6 cm with multiple large atypical polyps found inside the vagina. Cervix was healthy and os was closed. An excisional biopsy of the largest polyp was done and histopathology revealed benign fibroepithelial polyps. So decision was taken to allow spontaneous vaginal delivery. Since operative vaginal delivery should be avoided in such cases to reduce the risk of trauma and haemorrhage [1]. Her pregnancy continued well and she went in to spontaneous labour at 40+2 weeks. But caesarean section was done for intrapartum fetal distress. On follow up after 6 weeks, the patient is asymptomatic and the polyps were reduced in size and number which proved their hormone dependant nature [Table/Fig-2]. [Table/Fig-1]: Large pedunculated polyp with multiple fibroepithelial polyps of vagina [Table/Fig-2]: After 6 weeks polyps reduced in size and numbers Fibroepithelial polyps of the vagina (FEPV) are mucosal polypoid lesions with a connective tissue core covered by a benign squamous epithelium [2]. They are thought to be rare as few cases are reported in literature and the cases are compared with the present case in [Table/Fig-3]. [Table/Fig-3]: Comparison of reported cases in literature with the present case The aetiology of FEPV may be as a result of a granulation tissue reaction after some local injury of the vaginal mucosa. It is because of delayed differentiation of myofibroblastic stromal cells which explains why granulation tissue sometimes does not contract properly but turns into polyps [2]. But during pregnancy hormonal factors may modulate the growth of FEPVs. Hartmann CA et al., reported after examination with immunohistochemistry that FEPV expressed vimentin, desmin, and receptors for estrogen and progesterone which indicates the hormone dependant nature of these polyps [3]. Although benign, it can be confused with malignant connective tissue lesions because of its bizarre histology. The differential diagnoses are sarcoma botryoides, rhabdomyosarcoma and mixed mesodermal tumour [4]. Histopatholgy confirms the diagnosis. The other terminologies of FEPV reported in literature are Pseudosarcoma botryoides, Cellular pseudosarcomatous fibroepithelial stromal polyps and Polyposis vaginalis [5,6]. Treatment of FEPV is simple local excision [7,8]. It can be performed after pregnancy as an interval procedure when the vaginal vascularity has returned to normal. Recurrence is extremely uncommon [9]. Nucci MR et al., studied 65 cases of FEPV and reported that awareness of the spectrum of histopathologic features that these lesions can exhibit and is crucial in their accurate diagnosis thus avoiding potential overtreatment [5]. FEPV in pregnancy is a rare lesion. Although benign, it can be confused with some malignant tumours. Histopathology confirms the diagnosis. Treatment is simple local excision and recurrence is uncommon. Hence knowledge of clinical and histopathological features of these lesions is important for accurate diagnosis for avoiding potential overtreatment.

Using Invalid Instruments on Purpose: Focused Moment Selection and Averaging for GMM, Second Version

In finite samples, the use of a slightly endogenous but highly relevant instrument can reduce mean-squared error (MSE). Building on this observation, I propose a moment selection criterion for GMM in which moment conditions are chosen based on the MSE of their associated estimators rather than their validity: the focused moment selection criterion (FMSC). I then show how the framework used to derive the FMSC can address the problem of inference post-moment selection. Treating post-selection estimators as a special case of moment-averaging, in which estimators based on different moment sets are given data-dependent weights, I propose a simulation-based procedure to construct valid confidence intervals for a variety of formal and informal moment-selection and averaging procedures. Both the FMSC and confidence interval procedure perform well in simulations. I conclude with an empirical example examining the effect of instrument selection on the estimated relationship between malaria transmission and income.

Needleless laparoscopic abdominal cerclage placement.

To show a technique of laparoscopic interval abdominal cerclage placement with the use of a needleless mersilene tape. Step-by-step explanation of the technique using a surgical video. Cervical insufficiency affects 1% of all pregnancies and up to 8% of those with second and early third trimester losses. The abdominal method has been used in patients with an extremely short cervix in whom the transvaginal approach is not technically possible or for those who have experienced an unsuccessful transvaginal procedure. With the introduction of the transabdominal cerclage, the fetal survival rate improved from 21% to 89%. In an attempt to decrease the surgical morbidity associated with laparotomy, there have been multiple case series and cohort studies in the literature that described the laparoscopic approach for transabdominal cerclage placement. Laparoscopic abdominal cerclage placement was performed as an interval procedure using needleless mersilene tape after meticulous skeletonization of the uterine vessels and formation of the peritoneal window. Laparoscopic abdominal cerclage was placed without any complications, providing the patient with the benefits of minimally invasive approach. The risk of bleeding was reduced by meticulous dissection and skeletonization of uterine vessels and eliminating the use of the mersilene tape needle.

Needleless Laparoscopic Abdominal Cerclage Placement

Patient was a 30 yo G2P0020 with cervical incompetence who failed vaginal cerclage in her prior pregnancy. She was referred for laparoscopic abdominal cerclage placement as an interval procedure.

Preliminary results of a two-interval forced-choice method for assessing infant hearing sensitivity

Current methods for assessing infants' hearing are yes-no, single interval procedures. Although bias-free statistics can be used to describe the results of such procedures, with the limited number of trials typically available from an individual infant, use of these statistics can be problematic. A two-interval forced choice method based on infants' anticipatory eye movements toward an interesting visual event is currently under development. Preliminary results indicate that a high proportion of both 3- and 7-month-old infants achieve over 80% correct in the detection of a 70 dB SPL 1000 Hz tone presented through an insert earphone. Infants continue to perform better than expected by chance at levels as low as 25 dB SPL. Thus, a test method based on infant eye movements holds potential as an efficient behavioral method for assessing infant hearing.

Confidence intervals for a difference between lognormal means in cluster randomization trials.

Cluster randomization trials, in which intact social units are randomized to different interventions, have become popular in the last 25 years. Outcomes from these trials in many cases are positively skewed, following approximately lognormal distributions. When inference is focused on the difference between treatment arm arithmetic means, existent confidence interval procedures either make restricting assumptions or are complex to implement. We approach this problem by assuming log-transformed outcomes from each treatment arm follow a one-way random effects model. The treatment arm means are functions of multiple parameters for which separate confidence intervals are readily available, suggesting that the method of variance estimates recovery may be applied to obtain closed-form confidence intervals. A simulation study showed that this simple approach performs well in small sample sizes in terms of empirical coverage, relatively balanced tail errors, and interval widths as compared to existing methods. The methods are illustrated using data arising from a cluster randomization trial investigating a critical pathway for the treatment of community acquired pneumonia.

What is the effect of noise on the interval timing neural network?

Cognitive processes, such as decision making, rate calculation and planning, are strongly affected by the ability of subjects to perceive durations in the seconds-to-hours range (interval timing) [1]. A classic interval timing paradigm is the peak interval (PI) procedure which consists of interspersed reinforced and probe trials. During the reinforced trials, a stimulus such as a tone or light is turned on to signal the beginning of the to-be-timed interval and the subject’s first response after the criterion time is reinforced. During the probe trials, no reinforcement is given and the stimulus remains on for about three times the criterion time [2]. The mean response rate over a very large number of trials has a Gaussian shape whose peak measures the accuracy of criterion time estimation and the spread of the timing function measures its precision. In the vast majority of species, protocols, and manipulations to date, interval timing is both accurate and time-scale invariant, i.e. time-estimation errors increase linearly with the estimated duration [3]. We used a computational model of interval timing that mimics the activity of cortico-striatal structures involved in interval timing known as striatal beat frequency (SBF) model (Figure ​(Figure1)1) [4]. In mammals, administration of DA agonist, e.g., methamphetamine or cocaine produce an immediate, scalar (proportional), leftward shift in perceived time (responding earlier in time than under control conditions) whereas DA antagonist, e.g., haloperidol, has an opposed effect. Upon chronic administration of DA drugs, the timing functions recalibrate, i.e., they shift back to the values prior to drug administration. Once the drug is discontinued, the timing functions rebound (in a scalar manner) in the opposite direction from the initial effects of the drug, which is a signature of the clock pattern. SBF model can mimic clock patterns by adjusting the firing rates of FC neurons proportional to dopamine levels. The frequency modulation by dopaminergic drugs also produces a Gaussian-like output in SBF model. However, behavioral experiments indicate that although the average responses in PI procedure follow an almost Gaussian curve, there is always a notable skewness and a long tail of the output function. We found that frequency variability (noise) determines the deviation form the Gaussian-like output. Figure 1 (A) Schematic representation of the two main areas involved in interval timing: frontal cortex (FC) and basal ganglia (BG). (B) SBF model consists of a set of cortical oscillators, a reference memory that stores the state of the system at reinforcement ...

Selecting Stopping Rules for Confidence Interval Procedures

The sample size decision is crucial to the success of any sampling experiment. More samples imply better confidence and precision in the results, but require higher costs in terms of time, computing power, and money. Analysts often choose sequential stopping rules on an ad hoc basis to obtain confidence intervals with desired properties without requiring large sample sizes. However, the choice of stopping rule can affect the quality of the interval produced in terms of the coverage, precision, and replication cost. This article introduces methods for choosing and evaluating stopping rules for confidence interval procedures. We develop a general framework for assessing the quality of a broad class of stopping rules applied to independent and identically distributed data. We introduce coverage profiles that plot the coverage according to the stopping time and reveal situations when the coverage could be unexpectedly low. Finally, we recommend simple techniques for obtaining acceptable or optimal rules.