Customers often have to wait during the process of acquiring and consuming many products and services. These waiting experiences are typically negative and have been known to affect customers' overall satisfaction with the product or service. To better manage these waiting experiences, many firms have instituted a variety of programs not only to reduce the actual duration of the wait but also to improve customers' perceptions of it. In this paper, we examine the impact of one such initiative, namely, the institution of a waiting time guarantee, on customers' waiting experiences. A waiting time guarantee is a commitment from a firm to serve its customers within a specified period of time. If the firm fails to meet this commitment for some customers then it compensates them for the delay. Today, a large number of firms in a variety of industries such as fast food, banking, industrial distribution, and healthcare offer such time guarantees to their customers. We develop a utility theory-based model of customers' satisfaction with waiting in line. The model is based upon the assumption that when a customer joins a queue he or she has some prior beliefs about the distribution of service times at the firm. The customer estimates the likely duration of the waiting time on the basis of these beliefs about the service times and the observed queue length. We further assume that as the customer observes the service times for other customers who are ahead in the queue, he or she successively updates these beliefs about the distribution of service times in a Bayesian manner. We then posit that the customer's satisfaction both during as well as the end of the wait is determined by the difference between the customer's updated and the prior estimates of the total waiting time. We apply the model to derive select hypotheses pertaining to the impact of a waiting time guarantee on customers' waiting experiences. These hypotheses are based upon the assumption that an offer of a time guarantee is a signal of reliability from the firm and reduces customers' perceived variance around the expected service times. We empirically test these hypotheses using data from a series of interactive, computer-based laboratory experiments. In these experiments, we used the computer to create animations of reallife waiting experiences. The computer display consisted of a queue of customers waiting for service at a counter. One of the customers represented the participant in the experiment. During the course of the experiment, each participant joined the queue, waited in line for service, and then exited the system. At several points during the wait, each participant reported his or her level of satisfaction with the waiting experience. Our results suggest that if customers observe the service times to be less than expected, their satisfaction increases monotonically during the wait. Further, under such circumstances, the explicit provision of a waiting time guarantee enhances satisfaction both during as well as at the end of the wait. However, if customers observe the service times to be more than expected, then their satisfaction typically declines at the beginning of the wait but increases toward the end of the wait. Further, under these circumstances, the initial positive impact of the provision of a waiting time guarantee declines over time. Moreover, at the end of the wait, customers in guaranteed environments are actually less satisfied than those in unguaranteed environments. Overall, we find that a time guarantee, if met, increases satisfaction at the end of a wait; however, if violated, then it decreases satisfaction at the end of the wait. We discuss the implications of these and other empirical findings for the management of customers' waiting experiences.
Web users often face a long waiting time for downloading Web pages. Although various technologies and techniques have been implemented to alleviate the situation and to comfort the impatient users, little research has been done to assess what constitutes an acceptable and tolerable waiting time for Web users. This research reviews the literature on computer response time and users' waiting time for download of Web pages, and assesses Web users' tolerable waiting time in information retrieval. It addresses the following questions through an experimental study: What is the effect of feedback on users' tolerable waiting time? How long are users willing to wait for a Web page to be downloaded before abandoning it? The results from this study suggest that the presence of feedback prolongs Web users' tolerable waiting time and the tolerable waiting time for information retrieval is approximately 2 s.
OBJECTIVE: To investigate the efficacy of physiotherapy compared with a wait and see approach or corticosteroid injections over 52 weeks in tennis elbow. DESIGN: Single blind randomised controlled trial. SETTING: Community setting, Brisbane, Australia. PARTICIPANTS: 198 participants aged 18 to 65 years with a clinical diagnosis of tennis elbow of a minimum six weeks' duration, who had not received any other active treatment by a health practitioner in the previous six months. INTERVENTIONS: Eight sessions of physiotherapy; corticosteroid injections; or wait and see. MAIN OUTCOME MEASURES: Global improvement, grip force, and assessor's rating of severity measured at baseline, six weeks, and 52 weeks. RESULTS: Corticosteroid injection showed significantly better effects at six weeks but with high recurrence rates thereafter (47/65 of successes subsequently regressed) and significantly poorer outcomes in the long term compared with physiotherapy. Physiotherapy was superior to wait and see in the short term; no difference was seen at 52 weeks, when most participants in both groups reported a successful outcome. Participants who had physiotherapy sought less additional treatment, such as non-steroidal anti-inflammatory drugs, than did participants who had wait and see or injections. CONCLUSION: Physiotherapy combining elbow manipulation and exercise has a superior benefit to wait and see in the first six weeks and to corticosteroid injections after six weeks, providing a reasonable alternative to injections in the mid to long term. The significant short term benefits of corticosteroid injection are paradoxically reversed after six weeks, with high recurrence rates, implying that this treatment should be used with caution in the management of tennis elbow.
Intermittently connected mobile networks are sparse wireless networks where most of the time there does not exist a complete path from the source to the destination. These networks fall into the general category of Delay Tolerant Networks. There are many real networks that follow this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail.To deal with such networks researchers have suggested to use flooding-based routing schemes. While flooding-based schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention, which can significantly degrade their performance. Furthermore, proposed efforts to significantly reduce the overhead of flooding-based schemes have often be plagued by large delays. With this in mind, we introduce a new routing scheme, called Spray and Wait, that "sprays" a number of copies into the network, and then "waits" till one of these nodes meets the destination.Using theory and simulations we show that Spray and Wait outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered; its overall performance is close to the optimal scheme. Furthermore, it is highly scalable retaining good performance under a large range of scenarios, unlike other schemes. Finally, it is simple to implement and to optimize in order to achieve given performance goals in practice.
This article interrogates the corporeal experience of the event of waiting during the process of journeying. Rather than focusing on differential speed as central to charting the contingent relationality between mobilities and immobilities as has been the dominant mode of reasoning in mobility studies, I argue for a renewed focus on the body, specifically through the relationality between activity and inactivity. In this way, the event of waiting is no longer conceptualised as a dead period of stasis or stilling, or even a slower urban rhythm, but is instead alive with the potential of being other than this. Through an appreciation of the dynamic nature of temporality, this essay charts a journey through the relative in/activities embodied through waiting and concludes that waiting as an event should be conceptualised not solely as an active achievement or passive acquiescence but as a variegated affective complex where experience folds through and emerges from a multitude of different planes.
Over the past decade, many OECD countries have introduced new policies to tackle excessive waiting times for elective surgery with some success. However, in the wake of the recent economic downturn and severe pressures on public budgets, waiting times times may rise again, and it is important to understand which policies work. In addition, the European Union has introduced new regulations to allow patients to seek care in other member states, if there are long delays in treatment.  This book provides a framework to understand why there are waiting lists for elective surgery in some OECD countries and not in others. It also describes how waiting times are measured in OECD countries, which differ widely, and makes recommendations for best practice. Finally, it reviews different policy approaches to tackling excessive waiting times. Some countries have introduced guarantees to patients that they will not wait too long for treatment. These policies work only if they are accompanied by sanctions on health providers to ensure the guarantee is met or if they allow greater choice of health-care providers including the private sector. Many countries have also introduced policies to expand supply of surgical services, but these policies have generally not succeeded in the long-term in bringing down waiting times. Given the increasing demand for elective surgery, some countries have experimented with policies to improve priorisation of who is entitled to elective surgery. These policies are promising, but difficult to implement.
BACKGROUND: This study examined the relationship between patient waiting time and willingness to return for care and patient satisfaction ratings with primary care physicians. METHODS: Cross-sectional survey data on a convenience sample of 5,030 patients who rated their physicians on a web-based survey developed to collect detailed information on patient experiences with health care. The survey included self-reported information on wait times, time spent with doctor, and patient satisfaction. RESULTS: Longer waiting times were associated with lower patient satisfaction (p < 0.05), however, time spent with the physician was the strongest predictor of patient satisfaction. The decrement in satisfaction associated with long waiting times is substantially reduced with increased time spent with the physician (5 minutes or more). Importantly, the combination of long waiting time to see the doctor and having a short doctor visit is associated with very low overall patient satisfaction. CONCLUSION: The time spent with the physician is a stronger predictor of patient satisfaction than is the time spent in the waiting room. These results suggest that shortening patient waiting times at the expense of time spent with the patient to improve patient satisfaction scores would be counter-productive.
Importance: Although wait times for hip fracture surgery have been linked to mortality and are being used as quality-of-care indicators worldwide, controversy exists about the duration of the wait that leads to complications. Objective: To use population-based wait-time data to identify the optimal time window in which to conduct hip fracture surgery before the risk of complications increases. Design, Setting, and Participants: Population-based, retrospective cohort study of adults undergoing hip fracture surgery between April 1, 2009, and March 31, 2014, at 72 hospitals in Ontario, Canada. Risk-adjusted restricted cubic splines modeled the probability of each complication according to wait time. The inflection point (in hours) when complications began to increase was used to define early and delayed surgery. To evaluate the robustness of this definition, outcomes among propensity-score matched early and delayed surgical patients were compared using percent absolute risk differences (RDs, with 95% CIs). Exposure: Time elapsed from hospital arrival to surgery (in hours). Main Outcomes and Measures: Mortality within 30 days. Secondary outcomes included a composite of mortality or other medical complications (myocardial infarction, deep vein thrombosis, pulmonary embolism, and pneumonia). Results: Among 42 230 patients with hip fracture (mean [SD] age, 80.1 years [10.7], 70.5% women) who met study entry criteria, overall mortality at 30 days was 7.0%. The risk of complications increased when wait times were greater than 24 hours, irrespective of the complication considered. Compared with 13 731 propensity-score matched patients who received surgery earlier, 13 731 patients who received surgery after 24 hours had a significantly higher risk of 30-day mortality (898 [6.5%] vs 790 [5.8%]; % absolute RD, 0.79; 95% CI, 0.23-1.35) and the composite outcome (1680 [12.2%]) vs 1383 [10.1%]; % absolute RD, 2.16; 95% CI, 1.43-2.89). Conclusions and Relevance: Among adults undergoing hip fracture surgery, increased wait time was associated with a greater risk of 30-day mortality and other complications. A wait time of 24 hours may represent a threshold defining higher risk.
A wait-free implementation of a concurrent data object is one that guarantees that any process can complete any operation in a finite number of steps, regardless of the execution speeds of the other processes. The problem of constructing a wait-free implementation of one data object from another lies at the heart of much recent work in concurrent algorithms, concurrent data structures, and multiprocessor architectures. First, we introduce a simple and general technique, based on reduction to a concensus protocol, for proving statements of the form, “there is no wait-free implementation of X by Y.” We derive a hierarchy of objects such that no object at one level has a wait-free implementation in terms of objects at lower levels. In particular, we show that atomic read/write registers, which have been the focus of much recent attention, are at the bottom of the hierarchy: thay cannot be used to construct wait-free implementations of many simple and familiar data types. Moreover, classical synchronization primitives such as test&set and fetch&add , while more powerful than read and write , are also computationally weak, as are the standard message-passing primitives. Second, nevertheless, we show that there do exist simple universal objects from which one can construct a wait-free implementation of any sequential object.
An important class of machine scheduling problems is characterized by a no-wait or blocking production environment, where there is no intermediate buffer between machines. In a no-wait environment, a job must be processed from start to completion, without any interruption either on or between machines. Blocking occurs when a job, having completed processing on a machine, remains on the machine until a downstream machine becomes available for processing. A no-wait or blocking production environment typically arises from characteristics of the processing technology itself, or from the absence of storage capacity between operations of a job. In this review paper, we describe several well-documented applications of no-wait and blocking scheduling models and illustrate some ways in which the increasing use of modern manufacturing methods gives rise to other applications. We review the computational complexity of a wide variety of no-wait and blocking scheduling problems and describe several problems which remain open as to complexity. We study several deterministic flowshop, jobshop, and openshop problems and describe efficient and enumerative algorithms, as well as heuristics and results about their performance. The literature on stochastic no-wait and blocking scheduling problems is also reviewed. Finally, we provide some suggestions for future research directions.
BACKGROUND: Radical prostatectomy is widely used in the treatment of early prostate cancer. The possible survival benefit of this treatment, however, is unclear. We conducted a randomized trial to address this question. METHODS: From October 1989 through February 1999, 695 men with newly diagnosed prostate cancer in International Union against Cancer clinical stage T1b, T1c, or T2 were randomly assigned to watchful waiting or radical prostatectomy. We achieved complete follow-up through the year 2000 with blinded evaluation of causes of death. The primary end point was death due to prostate cancer, and the secondary end points were overall mortality, metastasis-free survival, and local progression. RESULTS: During a median of 6.2 years of follow-up, 62 men in the watchful-waiting group and 53 in the radical-prostatectomy group died (P=0.31). Death due to prostate cancer occurred in 31 of 348 of those assigned to watchful waiting (8.9 percent) and in 16 of 347 of those assigned to radical prostatectomy (4.6 percent) (relative hazard, 0.50; 95 percent confidence interval, 0.27 to 0.91; P=0.02). Death due to other causes occurred in 31 of 348 men in the watchful-waiting group (8.9 percent) and in 37 of 347 men in the radical-prostatectomy group (10.6 percent). The men assigned to surgery had a lower relative risk of distant metastases than the men assigned to watchful waiting (relative hazard, 0.63; 95 percent confidence interval, 0.41 to 0.96). CONCLUSIONS: In this randomized trial, radical prostatectomy significantly reduced disease-specific mortality, but there was no significant difference between surgery and watchful waiting in terms of overall survival.
BACKGROUND: Transurethral resection of the prostate is the most common surgical treatment for benign prostatic hyperplasia. We conducted a multicenter randomized trial to compare this surgery with watchful waiting in men with moderate symptoms of benign prostatic hyperplasia. METHODS: Of 800 men over the age of 54 years who were screened between July 1986 and July 1989, 556 (mean [+/- SD] age, 66 +/- 5 years) were studied (280 in the surgery group and 276 in the watchful-waiting group). Patients' symptoms and the degree to which they were bothered by urinary difficulties were measured with standardized questionnaires and medical evaluations. The primary outcome measure was treatment failure, which was defined as the occurrence of any of the following: death, repeated or intractable urinary retention, a residual urinary volume over 350 ml, the development of bladder calculus, new and persistent incontinence, a high symptom score, or a doubling of the serum creatinine concentration. Patients were followed for three years. RESULTS: Of the men randomly assigned to the surgery group, 249 underwent surgery within two weeks after the assignment. Surgery was not associated with impotence or urinary incontinence. The average follow-up period was 2.8 years. In an intention-to-treat analysis, there were 23 treatment failures in the surgery group, as compared with 47 in the watchful-waiting group (relative risk, 0.48; 95 percent confidence interval, 0.30 to 0.77). Of the men assigned to the watchful-waiting group, 65 (24 percent) underwent surgery within three years after the assignment. Surgery was associated with improvement in symptoms and in scores for urinary difficulties and interference with activities of daily living (P < 0.001 for all comparisons). The outcomes of surgery were best for the men who were most bothered by urinary symptoms at base line. CONCLUSIONS: For men with moderate symptoms of benign prostatic hyperplasia, surgery is more effective than watchful waiting in reducing the rate of treatment failure and improving genitourinary symptoms. Watchful waiting is usually a safe alternative for men who are less bothered by urinary difficulty or who wish to delay surgery.
In this paper, we describe ZooKeeper, a service for coordinating processes of distributed applications. Since ZooKeeper is part of critical infrastructure, ZooKeeper aims to provide a simple and high performance kernel for building more complex coordination primitives at the client. It incorporates elements from group messaging, shared registers, and distributed lock services in a replicated, centralized service. The interface exposed by Zoo-Keeper has the wait-free aspects of shared registers with an event-driven mechanism similar to cache invalidations of distributed file systems to provide a simple, yet powerful coordination service. The ZooKeeper interface enables a high-performance service implementation. In addition to the wait-free property, ZooKeeper provides a per client guarantee of FIFO execution of requests and linearizability for all requests that change the ZooKeeper state. These design decisions enable the implementation of a high performance processing pipeline with read requests being satisfied by local servers. We show for the target workloads, 2:1 to 100:1 read to write ratio, that ZooKeeper can handle tens to hundreds of thousands of transactions per second. This performance allows ZooKeeper to be used extensively by client applications. 1
OBJECTIVE: The objective of this study was to assess the effects of participation in a mindfulness meditation-based stress reduction program on mood disturbance and symptoms of stress in cancer outpatients. METHODS: A randomized, wait-list controlled design was used. A convenience sample of eligible cancer patients enrolled after giving informed consent and were randomly assigned to either an immediate treatment condition or a wait-list control condition. Patients completed the Profile of Mood States and the Symptoms of Stress Inventory both before and after the intervention. The intervention consisted of a weekly meditation group lasting 1.5 hours for 7 weeks plus home meditation practice. RESULTS: Ninety patients (mean age, 51 years) completed the study. The group was heterogeneous in type and stage of cancer. Patients' mean preintervention scores on dependent measures were equivalent between groups. After the intervention, patients in the treatment group had significantly lower scores on Total Mood Disturbance and subscales of Depression, Anxiety, Anger, and Confusion and more Vigor than control subjects. The treatment group also had fewer overall Symptoms of Stress; fewer Cardiopulmonary and Gastrointestinal symptoms; less Emotional Irritability, Depression, and Cognitive Disorganization; and fewer Habitual Patterns of stress. Overall reduction in Total Mood Disturbance was 65%, with a 31% reduction in Symptoms of Stress. CONCLUSIONS: This program was effective in decreasing mood disturbance and stress symptoms in both male and female patients with a wide variety of cancer diagnoses, stages of illness, and ages. cancer, stress, mood, intervention, mindfulness.
PURPOSE: Neoadjuvant chemoradiotherapy for rectal cancer can result in complete disappearance of tumor and involved nodes. In patients without residual tumor on imaging and endoscopy (clinical complete response [cCR]) a wait-and-see-policy (omission of surgery with follow-up) might be considered instead of surgery. The purpose of this prospective cohort study was to evaluate feasibility and safety of a wait-and-see policy with strict selection criteria and follow-up. PATIENTS AND METHODS: Patients with a cCR after chemoradiotherapy were prospectively selected for the wait-and-see policy with magnetic resonance imaging (MRI) and endoscopy plus biopsies. Follow-up was performed 3 to 6 monthly and consisted of MRI, endoscopy, and computed tomography scans. A control group of patients with a pathologic complete response (pCR) after surgery was identified from a prospective cohort study. Functional outcome was measured with the Memorial Sloan-Kettering Cancer Center (MSKCC) bowel function questionnaire and Wexner incontinence score. Long-term outcome was estimated by using Kaplan-Meier curves. RESULTS: Twenty-one patients with cCR were included in the wait-and-see policy group. Mean follow-up was 25 ± 19 months. One patient developed a local recurrence and had surgery as salvage treatment. The other 20 patients are alive without disease. The control group consisted of 20 patients with a pCR after surgery who had a mean follow-up of 35 ± 23 months. For these patients with a pCR, cumulative probabilities of 2-year disease-free survival and overall survival were 93% and 91%, respectively. CONCLUSION: A wait-and-see policy with strict selection criteria, up-to-date imaging techniques, and follow-up is feasible and results in promising outcome at least as good as that of patients with a pCR after surgery. The proposed selection criteria and follow-up could form the basis for future randomized studies.
In this paper, we study how to optimally manage the freshness of information updates sent from a source node to a destination via a channel. A proper metric for data freshness at the destination is the age-of-information, or simply age, which is defined as how old the freshest received update is, since the moment that this update was generated at the source node (e.g., a sensor). A reasonable update policy is the zero-wait policy, i.e., the source node submits a fresh update once the previous update is delivered, which achieves the maximum throughput and the minimum delay. Surprisingly, this zero-wait policy does not always minimize the age. This counter-intuitive phenomenon motivates us to study how to optimally control information updates to keep the data fresh and to understand when the zero-wait policy is optimal. We introduce a general age penalty function to characterize the level of dissatisfaction on data staleness and formulate the average age penalty minimization problem as a constrained semi-Markov decision problem with an uncountable state space. We develop efficient algorithms to find the optimal update policy among all causal policies and establish sufficient and necessary conditions for the optimality of the zero-wait policy. Our investigation shows that the zero-wait policy is far from the optimum if: 1) the age penalty function grows quickly with respect to the age; 2) the packet transmission times over the channel are positively correlated over time; or 3) the packet transmission times are highly random (e.g., following a heavy-tail distribution).
We report a randomized, wait-list controlled trial assessing the effects of school-wide positive behavior support (SWPBS). An effectiveness analysis was conducted with elementary schools in Hawaii and Illinois where training and technical assistance in SWPBS was provided by regular state personnel over a 3-year period. Results document that the training and technical assistance were functionally related to improved implementation of universal-level SWPBS practices. Improved use of SWPBS was functionally related to improvements in the perceived safety of the school setting and the proportion of third graders meeting or exceeding state reading assessment standards. Results also document that levels of office discipline referrals were comparatively low, but the absence of experimental control for this variable precludes inference about the impact of SWPBS. Implications for future research directions are offered.
Cancer results from genetic alterations that disturb the normal cooperative behavior of cells. Recent high-throughput genomic studies of cancer cells have shown that the mutational landscape of cancer is complex and that individual cancers may evolve through mutations in as many as 20 different cancer-associated genes. We use data published by Sjöblom et al. (2006) to develop a new mathematical model for the somatic evolution of colorectal cancers. We employ the Wright-Fisher process for exploring the basic parameters of this evolutionary process and derive an analytical approximation for the expected waiting time to the cancer phenotype. Our results highlight the relative importance of selection over both the size of the cell population at risk and the mutation rate. The model predicts that the observed genetic diversity of cancer genomes can arise under a normal mutation rate if the average selective advantage per mutation is on the order of 1%. Increased mutation rates due to genetic instability would allow even smaller selective advantages during tumorigenesis. The complexity of cancer progression can be understood as the result of multiple sequential mutations, each of which has a relatively small but positive effect on net cell growth.
What are the social consequences of the recent expansion of newborn screening in the United States? The adoption of new screening technologies has generated diagnostic uncertainty about the nature of screening targets, making it unclear not only whether a newborn will develop a disease but also what the condition actually is. Based on observations in a genetics clinic and in-depth interviews with parents and geneticists, we examine how parents and clinical staff work out the social significance of uncertain newborn screening results. We find that some newborns will experience a specific trajectory of prolonged liminality between a state of normal health and pathology. Based on a review of related literatures, we suggest "patients-in-waiting" as an umbrella concept for those under medical surveillance between health and disease.
The truth of this assertion cannot be denied: there can be few consumers of services in a modern society who have not felt, at one time or another, each of the emotions identified by Federal Express' copywriters. What is more, each of us who can recall such experiences can also attest to the fact that the waiting-line experience in a service facility significantly affects our overall perceptions of the quality of service provided.