ELICITING A DIRECTED ACYCLIC GRAPH FOR A MULTIVARIATE TIME SERIES OF VEHICLE COUNTS IN A TRAFFIC NETWORK

The problem of modelling multivariate time series of vehicle counts in traffic networks is considered. It is proposed to use a model called the linear multiregression dynamic model (LMDM). The LMDM is a multivariate Bayesian dynamic model which uses any conditional independence and causal structure across the time series to break down the complex multivariate model into simpler univariate dynamic linear models. The conditional independence and causal structure in the time series can be represented by a directed acyclic graph (DAG). The DAG not only gives a useful pictorial representation of the multivariate structure, but it is also used to build the LMDM. Therefore, eliciting a DAG which gives a realistic representation of the series is a crucial part of the modelling process. A DAG is elicited for the multivariate time series of hourly vehicle counts at the junction of three major roads in the UK. A flow diagram is introduced to give a pictorial representation of the possible vehicle routes through the network. It is shown how this flow diagram, together with a map of the network, can suggest a DAG for the time series suitable for use with an LMDM.     

A KNOWLEDGE-BASED DSS FOR MANAGERIAL PROBLEM DIAGNOSIS

A knowledge-based system supporting managerial problem diagnosis is described. The system provides the capability to monitor values of selected variables for problem situations. When problems are located, a list of problem symptoms is delivered to a problem processor for structuring and diagnosis. Problem structuring is based on a combination of concepts from expert systems and structural modeling. User assertions about cause-effect relationships between pairs of variables are maintained in a semantic network. Problem diagnosis uses the relationships in the semantic network to construct causation trees, the branches of which represent potential explanations of the problem symptoms. Mathematical models are constructed based on causation-tree branches, and values from the data base are used to test whether the model confirms the diagnosis. If so, the source of the problem has been located and it is then up to the user to resolve the problem. If the model fails to explain the problem, the model apparently is deficient and the user may perform “what if…” type scenarios in attempts to improve the model and search for problem causes. Realistic applications in the accounting and health care areas are discussed.     

The Invisible Village: An Exploration of Undergraduate Student Mothers’ Experiences

This study explored the experiences of mothers in college using a qualitative design. Results showed that a lack of financial resources was the chief barrier for student mothers in their educational pursuits while social/emotional support was the most important contributor to student mothers’ success in college. Participants relied heavily on student loans to cover costs of childcare or family to help watch their children. Role conflict experienced by student mothers has implications on family and college retention. Implications of this study included the adaptation and revisions of policies at the state and federal levels in addition to implications at the university level. Limitations of the study included a lack of racial and ethnic diversity and only including student mothers currently enrolled in college. Several recommendations for future research are described.     

Does IO Economics Really Make the Case for Investments in IT: A Rejoinder

The preceding critique [1] of the paper “The Information Problems in Organizations: A Research Model for the Value of Information and Information Systems” [3], reaches general conclusions with respect to the original paper and the applicability of economics to MIS research. These conclusions are based on arguments developed at a different level of analysis than that used in the original paper, and without considering the goals and intent of the original paper. The differences between the critique and the original paper are highlighted.     

Government Capital,Intimate and Community Social Capital,and Food Security Status in Older Adults with Different Income Levels

Whether government‐based forms of food assistance such as the Supplemental Nutrition Assistance Program (SNAP), communal efforts including food pantries, aid from friends and family, or alternative means such as gardening are the appropriate means to reduce the prevalence of household food insecurity is a continuous source of policy contention. To inform this debate, we examine the relative importance of these forms of food assistance and acquisition to a sample of U.S. older adults from the 2010 Brazos Valley Health Assessment of central Texas households that have been stratified by income eligibility for SNAP, low‐income SNAP ineligibility, and above low income status. To identify how membership in these socioeconomic groups constrains household capacity to acquire sufficient food to maintain an adequate and healthy diet, we explore the varied associations of assets received from government; communal and intimate social networks; and alternative food sources such as gardening, hunting, and fishing with household food security across socioeconomic status, while examining the importance of place of residence on the use of capital assets. SNAP participation was the only specific capital asset associated with all levels of food insecurity for both SNAP‐eligible and ineligible low‐income groups, thus emphasizing the continued importance of food assistance among poverty‐level older adults.     

Environmental Exposures to Metals in Native Communities and Implications for Child Development: Basis for the Navajo Birth Cohort Study

Two disparate statistics often cited for the Western United States raise concern about risks for developmental disabilities in Native American children. First, 13 of the states with the highest percentage of Native American population are located in the Western United States (U.S. Census Bureau, 2012 U.S. Census Bureau. (2012). The American Indian and Alaska Native Population: 2010 (U.S. Census Briefs, January, #C2010BR-10). Retrieved from http://www.census.gov/prod/cen2010/briefs/c2010br-10.pdf [Google Scholar]). Second, more than 161,000 abandoned hard-rock mines are located in 12 Western states (General Accounting Office, 2014 General Accounting Office. (2014, July 14). GAO-11–834T: Abandoned Mines. Information on the number of hardrock mines, cost of cleanup, and value of financial assurances. Statement of Anu K. Mittal, Director, Natural Resources and Environment Team, Testimony before the Subcommittee on Energy and Mineral Resources, Committee on Natural Resources, House of Representatives. Retrieved from http://www.gao.gov/products/GAO-11-834T [Google Scholar]). Moreover, numerous studies have linked low-level metals exposure with birth defects and developmental delays. Concern has emerged among tribal populations that metals exposure from abandoned mines might threaten development of future generations.     

An Experimental Analysis of Children's Dislike of Aggressors and Victims

We experimentally examined social contextual factors that might moderate children's dislike for aggressors and for victims of aggression, by varying both the aggressor's behavior (aggressive toward multiple children versus aggressive only toward one child) and the victim's behavior (passive versus assertive). Children (117 male and female fourth to sixth graders) listened to one of four scenarios describing the experiences of boys at a summer camp and rated how much they liked the aggressor, the victim, and the other children in the scenario; children also reported how much they thought the aggressor, victim, and others liked each other. Overall, and consistent with previous research, children disliked aggressors the most, followed by victims and then by the other children in the scenarios. Importantly, children's liking was influenced by the social context in which the aggression occurred, particularly in regards to how the victim responded. Aggressors (general or focused) were liked more if their victim was assertive rather than nonassertive. Furthermore, children liked nonassertive victims less than assertive victims, particularly a nonassertive victim in response to a general aggressor. Inferred liking among the group members also was dependent on the social context of the provocation. This research highlights the need to consider aggression as more than a set of behaviors. Aggression is a social event embedded within a social context and interpersonal relationships must be considered.     

Forecasting Multivariate Road Traffic Flows Using Bayesian Dynamic Graphical Models,Splines and Other Traffic Variables

Traffic flow data are routinely collected for many networks worldwide. These invariably large data sets can be used as part of a traffic management system, for which good traffic flow forecasting models are crucial. The linear multiregression dynamic model (LMDM) has been shown to be promising for forecasting flows, accommodating multivariate flow time series, while being a computationally simple model to use. While statistical flow forecasting models usually base their forecasts on flow data alone, data for other traffic variables are also routinely collected. This paper shows how cubic splines can be used to incorporate extra variables into the LMDM in order to enhance flow forecasts. Cubic splines are also introduced into the LMDM to parsimoniously accommodate the daily cycle exhibited by traffic flows. The proposed methodology allows the LMDM to provide more accurate forecasts when forecasting flows in a real high‐dimensional traffic data set. The resulting extended LMDM can deal with some important traffic modelling issues not usually considered in flow forecasting models. Additionally, the model can be implemented in a real‐time environment, a crucial requirement for traffic management systems designed to support decisions and actions to alleviate congestion and keep traffic flowing.