Reducing sample size needed for cox-proportional hazards model analysis using more efficient sampling method

Abstract

In general, survival data are time-to-event data, such as time to death, time to appearance of a tumor, or time to recurrence of a disease. Models for survival data have frequently been based on the proportional hazards model, proposed by Cox. The Cox model has intensive application in the field of social, medical, behavioral and public health sciences. In this paper we propose a more efficient sampling method of recruiting subjects for survival analysis. We propose using a Moving Extreme Ranked Set Sampling (MERSS) scheme with ranking based on an easy-to-evaluate baseline auxiliary variable known to be associated with survival time. This paper demonstrates that this approach provides a more powerful testing procedure as well as a more efficient estimate of hazard ratio than that based on simple random sampling (SRS). Theoretical derivation and simulation studies are provided. The Iowa 65+ Rural study data are used to illustrate the methods developed in this paper.     

Computer support of placement planning: the use of expert systems in child welfare

Computers have become commonplace in nearly every setting, from home to office. In addition to their usefulness for managerial tasks, they have the potential to aid the primary decision-making tasks of professional social service workers. The benefits and background of such "expert systems" are explored, and the structure of one experimental consulting program for child welfare workers, PLACECON, is presented.     

Mental Illness and Criminal Behavior

The tragic events in Aurora, CO and Newtown, CT have renewed public perception of mentally persons as ‘dangerous’ and ‘criminal.’ Unfortunately, this perception is based more on conjecture and fear than research. The following essay takes stock of the empirical research on mental illness and criminal behavior. Three noteworthy trends emerge from this literature. First, the prevalence of mental illness is substantially higher among individuals who have come in contact with the criminal justice system relative to the general population. Second, individuals with psychotic and externalizing behavioral disorders, particularly those who also abuse drugs and alcohol, tend to engage in higher levels of violence than individuals with other forms of mental illness. Third, mental illness does not determine whether someone will break the law; rather, it is but one of many criminogenic risk factors that interact in complex ways to influence individual behavior.     

Reputation spillover effects from grant‐providing institutions

There is a broad academic discussion about the impact of funding grants from a foundation or a government department on individual support intentions toward the nonprofit organization receiving the grant. However, the role of the grant provider's reputation has frequently been overlooked. In this study, we experimentally tested whether there is a reputation spillover effect of a grant‐providing organization. Based on a real‐life example, we asked citizens to rate their willingness to donate to a nonprofit organization, and we experimentally manipulated the available information on funding sources. We test this for both a government department and a foundation as a grant provider. Our results suggest that not the act of receiving a grant, but the citizens' awareness about the funding organization—at least in the case of a foundation—has an impact on support intentions. In contrast, for a prominent government department as a grant provider, we did not find support for a reputation spillover effect.     

Estimating urban lawn cover in space and time: Case studies in three Swedish cities

Lawns are considered monocultures and lesser contributors to sustainability than diverse nature but are still a dominating green area feature and an important cultural phenomenon in cities. Lawns have esthetical values, provide playground, are potential habitat for species, contribute to carbon sequestration and water infiltration, but also increase pesticides, fertilization, are monocultures and costly to manage at the same time. To evaluate the potential impact of lawns, whether positive or negative, it is of interest to estimate the total lawn cover in cities and its change over time. This is not a straightforward process, e.g., because many lawns are small and covered by trees. In this study we review the existing literature of lawn cover in cities and the different methodologies used for cover estimation. We found both pros and cons with NDVI and LiDAR data as well as manually interpreted aerial photos. The total cover of lawns in three case study cities was estimated to 22.5%. By extrapolating these percentages to all Swedish cities lawn cover was estimated to 2589 km² (0.6% of the terrestrial surface). The approximated total municipal management cost of lawns in all Swedish cities was 910,000,000 USD/ year. During 50 years lawn area almost doubled in relative cover and 56% of them were continuously managed. Since lawns constitute large parts of the urban greenery and are costly to manage it is highly relevant to consider their social, ecological and cultural value compared to alternatives, e.g., meadows with less intensive management.     

Are sponsors blamed for edging off? Consumer reactions to sponsorship terminations

Firms regularly terminate sponsorships, even without publicly known misconduct by the sponsee such as athlete doping. Consumer reactions to these sponsorship terminations by firms have not been studied despite being a regular occurrence. Using a set of experimental studies, this paper analyzes consumer reactions to these sponsorship terminations (i.e., early and non-renewal) that were not caused by a sponsee’s misconduct, the underlying process that causes the reactions, and the role of several moderating factors (trust, power balance, and locus of control). Our findings reveal that sponsorship terminations have a negative effect on sponsors’ brand images—particularly early terminations that occur before the end of a contract—because consumers perceive these sponsorship terminations as unfair. The results also suggest that a termination is particularly harmful for the sponsor’s perceived fairness if the sponsor is powerful and if the termination decision is under the sponsor’s control. Further, the termination effect is particularly strong for firms that consumers trust.     

A note on interdependent happiness

Based on two models of interdependent utilities [Becker, G., 1974. A theory of social interaction, Journal of Political Economy 82, 1064–1093; Fehr, E., Schmidt, K., 1999. A theory of fairness, competition, and cooperation, Quarterly Journal of Economics 114, 817–868] we derive a functional relationship between average happiness and the standard deviation of happiness within a country. This hypothesis is supported by an empirical investigation of 71 countries which shows that the average happiness in these countries depends only on income and on the standard deviation of happiness σ. The latter may be partly based on influences beyond income, for which no data are available. Income has the expected positive influence and σ has the expected negative influence, i.e. large differences in “autonomous” happiness have a dampening influence on “effective” happiness which also takes into account the happiness of others.     

Quality of Life Indexes for National Policy: Review and Agenda for Research

A number of governments and public policy institutes have developed Quality of Life Indexes – statistics that attempt to measure the quality of life for entire states or regions. We develop 14 criteria for determining the validity and usefulness of such QOL indexes to public policy. We then review 22 of the most-used QOL indexes from around the world. We conclude that many of the indexes are successful in that they are reliable, have established time series measures, and can be disaggregated to study subpopulations. However, many fall short in four areas: (1) indexes vary greatly in their coverage and definitions of domains of QOL, (2) none of the indexes distinguish among the concepts of input, throughput, and output that are used by public policy analysts, (3) they fail to show how QOL outputs are sensitive to public policy inputs, and (4) none have examined convergent validity against each other. We conclude that many of these indexes are potentially very useful for public policy and recommend research to further improve them.     

Mortality, fertility, education and capital accumulation in a simple OLG economy

We develop a simple OLG model to analytically show that aging leads to increased educational efforts through a general equilibrium effect. The mechanism is that scarcity of raw labor increases the return of human relative to physical capital. While a reduction in the birth rate is shown to unambiguously increase educational efforts, increases in the survival rate have ambiguous effects. Falling birth rates also increase capital per worker, but the effects of rising survival rates are again ambiguous. We conclude that our model is a useful laboratory to highlight potentially offsetting effects in models with endogenous education and overlapping generations.