Increasing the degrees of freedom in existing group randomized trials: the df* approach

This study describes a method for incorporating external estimates of intraclass correlation to improve the precision for the analysis of an existing group-randomized trial. The authors use a random-effects meta-analytic approach to pool the information across studies, which takes into account any interstudy heterogeneity that may exist. This approach can be used in several different situations to estimate the degrees of freedom available for an adjusted test of the intervention effect in a study where the challenges of group-randomized trials were not fully considered when the study was planned. The authors discuss the limitations of this approach and the circumstances in which it is likely to be helpful.     

Back to Inertia: Theoretical Implications of Alternative Styles of Logical Formalization

This article applies two new criteria, desirability and faithfulness, to evaluate Péli et al.'s (1994) formalization of Hannan and Freeman's structural inertia argument (1984, 1989). We conclude that this formalization fails to meet these criteria. We argue that part of the rational reconstruction on which this formalization builds does not reflect well the substantive argument in translating the natural language theory into logic. We propose two alternative formalizations that meet both of these criteria. Moreover, both derive the inertia theorem from much weaker, so much less constraining, premises. While both new formalizations draw information only from the original statement of the inertia theory, they reflect two different interpretations of inertia accumulation.
The two new formalizations are compatible with some recent theory extensions in organizational ecology. However, they lead to substantially different consequences when additional sociological considerations are added to their premise sets. The interplay between logical formalization and sociological content is highlighted using the example of Stinchcombe's (1965) liability-of-newness theorem. Even modest extensions of the proposed models lead to contrary implications about the age dependence in organizational mortality rates. Even faithful logical formalizations of arguments ordinarily involve implicit theory building.     

ON FUZZY GOAL PROGRAMMING*

This paper illustrates how the goal programming problem with fuzzy goals having linear membership functions may be formulated as a single goal programming problem. Also, a previously defined method for dealing with fuzzy weights for each of the goals is re-examined.     

这液体能替代食物吗

<正>Rob Rhinehart所尝试的自助式调配液体食品,并长期食用的做法,对于普通人来讲,却属于危险动作,必须要向读者强调请勿模仿。而且,据某松鼠透露,实验室的同事试着尝试了类似的营养液,七天后——差点儿没把自己恶心死。Rob Rhinehart已经尝试将自己的独家配方商品化,并已经募集了超过60万美元...     

The Organizational Niche

Although the concept of niche has been extremely useful in sociological theory and research, some aspects of the concept have not been clearly developed. This article advances a theoretical reconstruction of the concept of niche, with special application to organizations. The proposed formal model unifies several active lines of sociological theory. It also extends the notion of the niche from the realm of behaviors to apply to the rules coding social identities and organizational forms. The reconstruction gives deeper insight into the niche of an organizational population as well as individual organizations. Finally, the model analyzes the (thus far) tacit assumption that niches are convex, examines the implications of convexity for commonly used measures of niche width, and provides a general sociological argument for the predominance of convex niches.     

A NOTE ON ARMA PARAMETERISATION*

This paper considers the relationship between ARMA parameterisations of models for y(t) and Ay(t), where A is invertible and y(t) is a vector time series (t = 0,±1,…). An ARMA model for the transformed series Ay(t) may have fewer parameters than a model for y(t). This paper shows that such a saving is illusory because the apparently saved parameters are exactly balanced by the number of new parameters appearing in A.     

Increasing the degrees of freedom in future group randomized trials: the df* approach

This article builds on the previous article by Blitstein et al. (2005), which showed how external estimates of intraclass correlation can be used to improve the precision for the analysis of an existing group randomized trial. The authors extend that work to sample size estimation and power analysis for future group-randomized trials. Often this approach will allow a smaller study than would otherwise be possible without sacrificing statistical power. Such studies are needed, for example, as pilot studies to help plan for a full-scale efficacy trial, as replication studies, or in situations in which resource constraints prohibit a larger trial. The authors discuss the circumstances under which this strategy will be most helpful and the risks associated with conducting smaller studies.     

THE CONVERGENCE OF AUTOCORRELATIONS AND AUTOREGRESSIONS1

For a general class of scalar stationary processes, essentially those for which the best linear predictor is the best predictor (in the mean square sense), it is shown that, under fairly minor additional conditions, the sample autocorrelations converge to the true values almost surely and hniformly in the lag, t, at a rate (T^-1log T)^1/2, where T is the sample size. For ARMA processes, if |t|(log T)^a, a < ∞, the rate is the best possible, namely (T^-1log log T)^1/2. In particular the somewhat implausible condition, on the innovations, that E{ε(t)²| F_t-l} is constant is avoided in these results. The theorems are used to discuss autoregressive approximation. When the stationary process is a vector process the condition on the innovation sequence, ε(t), that E{ε(t)ε(t)| F_t-l} be constant, cannot be entirely avoided in relation to autoregressive approximation. This is also discussed.     

Local Environmental Groups: A Systematic Enumeration in Two Geographical Areas*

Abstract Local environmental groups, although acknowledged increasingly since the mid‐1980s, have not been sampled systematically, have been reported to consist of only a few types, and are often considered to be of only minor political significance. In this study we systematically inventoried all local environmental groups in two U.S. geographical areas: the Delmarva Peninsula and the state of North Carolina. We found 566 local groups, seven to 20 times the number reported in the best published directory. Three‐quarters did not fit the types most commonly characterized in the literature. Extrapolating from our study areas, we estimate that 16,000 to 30,000 local environmental groups are active in the United States. We find that these groups have a subset of “core” members, those active in organizing and local operations. We estimate the population of core members at 265,000 to 290,000, over 50 times the total of professional staff members of all U.S. national environmental organizations. These groups affect local and state environmental policy, enforcement of environmental laws, the shaping of environmental issues, and the social infrastructure for environmental behaviors.