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[The correlation of the indices of animal longevity and mortality in stationary populations with a constant rate of mortality].
Equations have been derived on the basis of general ratios of the numbers of different age groups of animals that allow to estimate the mortality coefficient in populations with stationary age structure and intensity of mortality that does not depend on age at their continuous and discontinuous replenishing by frequency of occurrence of individuals of the maximal age. The proposed method of estimation of mortality has been tested on models with different numbers of animals and age classes. The equation gives a non-biased estimate of mortality coefficient for populations with discontinuous replenishing with young individuals at very small sample sizes (less than 10 individuals).
The job market for newly licensed nurses.
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Nursepower: what do statistics reveal about the nation's nurses?
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Florence Nightingale: statistician and consultant epidemiologist.
Florence Nightingale became a legend in her own lifetime and the image of the lady with the lamp still influences public thinking about the practice of nursing and its practitioners. Like many legends, her story has been adapted to suit changing circumstances and purposes. One could speculate why it is that particular aspects have come into greater prominence at particular times in history. This article explores a less-known aspect of her work, her expertise and use of statistics and epidemiology. And it illustrates how that expertise was called upon to address a major health problem in New Zealand in 1860.
Examination of the generalized age distribution.
The formula for the age distribution and other relationships that follow from it for any (non-stable) population presented by Preston and Coale are significant contributions to demography. The formulas summarize the relationships among various demographic measures precisely, and are formally analogous to the relationships that hold for stable populations. The significance of these formulas cannot be overstated; they allow us to understand clearly the relationships among demographic measures in any arbitrary population. However, when it comes to using them for estimating demographic measures when census data are defective, the method of estimation is still affected by defective data. The reason is that the series of age-specific growth rates reflects the observed census age distributions exactly so that any defects in the census data are summarized in the growth rates. This paper begins with the formulation of the discrete version of the "new synthesis" developed by Preston and Coale. With the discrete formulation, the three kinds of errors introduced when the continuous time formulas are applied to real data can be avoided. Then it is pointed out that when two accurate census data are available, the Preston-Coale procedure of "estimating" the age distribution at the second census is equivalent to checking the identity of the age distribution formula. Also "estimating" mortality by the procedure of Preston-Coale is shown to be equivalent to obtaining mortality directly from intercensal survival rates. That the procedure which involves the age-specific growth rates is equivalent to those that involve the intercensal survival rates may have escaped notice because there are no a priori constraints for patterns of age-specific growth rates to follow. The irregularity in growth rates due to defective data are not distinguishable from true irregularity that exists in the population, contrary to the well-known regularity in the pattern of survival rates in human populations.
Geographic mobility of foreign medical graduates and the doctor shortage: a longitudinal analysis.
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Migration differentials by education and occupation: trends and variations.
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The analysis of linkages in demographic theory.
Many seemingly different questions that arise in the analysis of population change can be phrased as the same technical question: How, within a given demographic model, would variable y change if the age- or time-specific function f were to change arbitrarily in shape and intensity? At present demography lacks the machinery to answer this question in analytical and general form. This paper suggests a method based on modern functional calculus for deriving closed-form expressions for the sensitivity of demographic variables to changes in input functions or schedules. It uses this "linkage method" to obtain closed-form expressions for the response of the intrinsic growth rate, birth rate, and age composition of a stable population to arbitrary marginal changes in its age patterns of fertility and mortality. It uses it also to obtain expressions for the transient response of the age composition of a nonstable population to time-varying changes in the birth sequence, and to age-specific fertility and mortality patterns that change over time. The problem of "bias" in period vital rates is also looked at.
Population redistribution and changes in the size-density slope.
As regional population density increases territorial units tend to subdivide. For maximum societal time-efficiency the slope relating the logarithms of unit areas to those of unit densities should be -2/3. When boundaries become fixed, however, observed slopes tend to drift toward a value of zero. It was earlier hypothesized that such slope-erosion was due to increasing concentration of the population. Historical data for the primary political divisions of ten nations shows general support for the hypothesis.
[Statistics concerning population dynamics and the life table].
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Some further observations on the index of residential differentiation.
The relationship between the index of residential differentiation (RDI), a recently introduced measure of residential segregation which is designed to summarize the distribution of c social groups in a single index, and the indices of dissimilarity (D) and segregation (SI) is examined. It is demonstrated that RDI is a natural extension of D, and that when c = 2, RDI = D; when c greater than 2, it is possible to stipulate RDI in terms of SI, but it is not possible to stipulate RDI in a straightforward manner in terms of D. An adjusted RDI is then suggested in which random segregation rather than complete desegregation is used as the baseline.
The incidence of low birth weight: a critical review of available information.
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Community satisfaction, expectations of moving and migration.
A previous residential mobility model (Speare, 1974) assumes an additive relationship between residential satisfaction, desire to move, and mobility. This paper elaborates the model and applies it to intercounty migration. An interaction between community satisfaction and expectations to migrate is hypothesized which distinguishes four groups of decision makers. A survey in Durham, North Carolina and a unique mobility follow-up over eight years provide the data to test the model and the interaction. Furthermore, using various time periods for identifying migrants offers some methodological insights. Results support Speare's general formulation but only after the interaction is taken into account. A three-year migration interval is found to be appropriate.
[Population effects of fluctuation in fecundity and mortality in Triatoma infestans: simulation using Leslie matrices].
The population effects of known fluctuations in fecundity and mortality of T. infestans was studied through simulation using Leslie matrices. The effect of mortality and fecundity cycles was a stepped cycling through the growing phase, with no significant population decreases. Density dependent regulation stabilizes changes during the steady phase. The main effect is on population composition with the establishment of a regular annual cycle in the proportion of different age groups. Cycles with high number of larvae may be misinterpreted as an adult plague.
[Environmental radiations and childhood dynamic statistics (author's transl)].
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Looking for chaos in brain slices.
Many signals measured from the nervous system exhibit apparently random variability that is usually considered to be noise. The development of chaos theory has revealed that such random appearing variability may not, in fact, be random, but rather may be deterministic behavior that can reveal important information about the system's underlying mechanisms. We present some new methods for distinguishing determinism from randomness in experimental data, and we apply these methods to population neural responses recorded from hippocampal tissue slices.