RAND Corporation

About: RAND Corporation is a nonprofit organization based out in Santa Monica, California, United States. It is known for research contribution in the topics: Health care & Population. The organization has 9602 authors who have published 18570 publications receiving 744658 citations.

Constructing Maximal Dynamic Flows from Static Flows

Abstract: A network, in which two integers tij the traversal time and cij the capacity are associated with each arc PiPj, is considered with respect to the following question. What is the maximal amount of goods that can be transported from one node to another in a given number T of time periods, and how does one ship in order to achieve this maximum? A computationally efficient algorithm for solving this dynamic linear-programming problem is presented. The algorithm has the following features a The only arithmetic operations required are addition and subtraction b In solving for a given time period T, optimal solutions for all lesser time periods are a by-product c The constructed optimal solution for a given T is presented as a relatively small number of activities chain-flows which are repeated over and over until the end of the T periods. Hence, in particular, hold-overs at intermediate nodes are not required d Arcs which serve as bottlenecks for the flow are singled out, as well as the time periods in which they act as such e In solving the problem for successive values of T, stabilization on a set of chain-flows seec above eventually occurs, and an a priori bound on when stabilization occurs can be established. The fact that there exist solutions to this problem which have the simple form described in c is remarkable, since other dynamic linear-programming problems that have been studied do not enjoy this property.

Quality collaboratives: lessons from research

Abstract: Quality improvement collaboratives are increasingly being used in many countries to achieve rapid improvements in health care. However, there is little independent evidence that they are more cost effective than other methods, and little knowledge about how they could be made more effective. A number of systematic evaluations are being performed by researchers in North America, the UK, and Sweden. This paper presents the shared ideas from two meetings of these researchers. The evidence to date is that some collaboratives have stimulated improvements in patient care and organisational performance, but there are significant differences between collaboratives and teams. The researchers agreed on the possible reasons why some were less successful than others, and identified 10 challenges which organisers and teams need to address to achieve improvement. In the absence of more conclusive evidence, these guidelines are likely to be useful for collaborative organisers, teams and their managers and may also contribute to further research into collaboratives and the spread of innovations in health care.

The fitting of straight lines when both variables are subject to error

Abstract: Consider the situation where X and Y are related by Y = α + βX, where α and β are unknown and where we observe X and Y with error, i.e., we observe x = X + u and y = Y + v. Assume that Eu = Ev = 0 and that the errors (u and v) are uncorrelated with the true values (X and F). We survey and comment on the solutions to the problem of obtaining consistent estimates of α and β from a sample of (x, y)'s, (1) when one makes various assumptions about properties of the errors and the true values other than those mentioned above, and (2) when one has various kinds of “additional information” which aids in constructing these consistent estimates. The problems of obtaining confidence intervals for β and of testing hypotheses about β are not discussed, though approximate variances of some of the estimates of β are given. * This paper is an outgrowth of a Master's Thesis submitted to the Department of Statistics, University of Chicago. I am indebted for helpful comments and criticisms to T. E. Harris, W. H. Kr...

Sexual assault and mental disorders in a community population.

Abstract: A cross-sectional probability survey of 3132 household adults was conducted in two Los Angeles communities in order to examine the relationship between sexual assault and prevalence of 9 major mental disorders. Diagnoses of mental disorders were compared between those subjects who reported that they have experienced sexual abuse at some time in their lives and those who were not exposed to sexual assault. Disorders assessed include major depression mania schizophrenia alcohol abuse or dependence antisocial personality phobia panic disorder and obsessive-compulsive disorder. Findings revealed that 13.2% of the studied population have been experiencing lifetime sexual assault. Those who were exposed to childhood sexual abuse were more likely than those assaulted in adulthood to report the development of a mental disorder. Lifetime prevalences of affective disorder including major depressive and manic disorders and drug abuse or dependence as well as three anxiety disorders including phobia mania and obsessive-compulsive disorder were significantly higher among assaulted individuals. The risk ratios indicate that the onset of associated disorder after assault was 2.3-4.0 times greater among the assaulted group relative to the nonassaulted ones. However Hispanic ethnic background and education were unrelated to the occurrence of mental disorders following sexual assault.