Formtest räumlicher Punkthaufen bei beliebiger Population

In an eralier work [Landhäusser, 1973] the densities for the form variables ₂₁ ² , ₃₁ ² , ₃₂ ² were derived by means of the assumption of a population sphere. The variables cited represent the ratio of each two eigenvalues of the 3×3 matrixX, whose elements satisfy theWishart-density.In this wrok the densities for the form variables are invesigated while assuming an arbitrary populaion ellipsoid (Concentration ellipsoid) and for the resulting series an estimate fo the remainder is given. With the help of this estimate it is possible to establish an upper limit for the summation index. An evaluatio nis only possible when very fast machines are used.For the rotation ellipsoides one gains relatively simple results. The densities are give for ₂₁ ² . Possiblities for application of these densities can be found in the fields of geodesy and ballistics.A given target (e.g. an object in flight) is enveloped by a rotation ellipsoid whose half-axial rations are introduced into the densities as populations parameters. After determination of an error-probability the form of cluster of points can be tested for significance. Additional tests with regard to volume and center of a random-sample are possible.     

Estimation problems for rectangular distributions (or the taxi problem revisited)

The problem of estimating the unknown upper bound on the basis of a sample of sizen from a uniform or rectangular distribution on [0, ] has considerable interest. This or the analogous discrete version is variously known as the Taxi-problem or the German bomb (or Tank) problem and has a long history. The emphasis here is on estimation of through the lengths of the observed gaps or spacings which seem natural for this problem.     

Detecting Outliers in Frontier Models: A Simple Approach

In frontier analysis, most of the nonparametric approaches (DEA, FDH) are based on envelopment ideas which suppose that with probability one, all the observed units belong to the attainable set. In these deterministic frontier models, statistical theory is now mostly available (Simar and Wilson, 2000a). In the presence of super-efficient outliers, envelopment estimators could behave dramatically since they are very sensitive to extreme observations. Some recent results from Cazals et al. (2002) on robust nonparametric frontier estimators may be used in order to detect outliers by defining a new DEA/FDH deterministic type estimator which does not envelop all the data points and so is more robust to extreme data points. In this paper, we summarize the main results of Cazals et al. (2002) and we show how this tool can be used for detecting outliers when using the classical DEA/FDH estimators or any parametric techniques. We propose a methodology implementing the tool and we illustrate through some numerical examples with simulated and real data. The method should be used in a first step, as an exploratory data analysis, before using any frontier estimation.     

Sulla convergenza di un algoritmo di direzioni ammissibili per problemi di ottimo a vincoli lineari con funzione oggetto convessa non differenziabile

Se, essendof la funzione obiettivo del problema, {x ^k } e {f(x ^k )} sono le successioni delle approssimazioni rispettivamente di una soluzione ottimax ^* e dell' ottimof(x ^*) generate da un noto algoritmo di direzioni ammissibili a parametri antizigzag _k , mostriamo che per avere (a) lim _k f(x ^*)=f(x ^*) basta assumere lim _{k k} =0. Inoltre, ove si assuma in più la stretta convessità dif, si ha anche (b) lim _k x ^k =x ^*. Da quest'ultima condizione deriviamo infine specifiche ipotesi, in ordine alla (b), per il caso particolare del problema di trasporto stocastico.

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Summary The aim of the present paper is to analyze, without differentiability of the objective functionf, the convergence of a known «feasible directions» algorithm for constrained optimization problems having the constraints linear [8], 6.5.2.In these circumstances (i.e. iff is not differentiable) one must, almost in general, verify some preliminary conditions to obtain convergence [4]. Nevertheless, this work is not always easy to accomplish particularly in absence of differentiability.Here, we establish that under the convexity assumption forf, the only condition lim _{k k} =0, where the _k are the antizigzag parameters, suffices to obtain the convergence of the algorithm, i.e. lim _k f(x ^k )=opt., thex ^k being the approximate solutions to problem. The proof is obtained by application of the Th. 24.5, [6]. Successively, we consider the question if one has also the convergence of {x ^k } to optimal solution. By using now the Cor. 27.2.2, [6], we establish, for this purpose, that under an additional general qualification forf — precisely the strict convexity — the convergence of {x ^k } is also stated. Finally, we examine the above property for the stochastic transportation problem [1] for which we indicate special conditions in order to verify the latter convergence property.

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pervenuto il 28-4-82     

Interaction of human and physical capital in a model of endogenous growth

A model of development is presented where growth is initially driven by physical capital accumulation, as in the neoclassical model. After a critical level of physical capital is reached, the economy takes off and enters a stage of sustained growth driven by human capital accumulation. The link between these two stages is provided by the assumption that private incentives for human capital accumulation increase with the average levels of human and physical capital. At the early stages of development, these incentives are low so the level of human capital stays stagnant until sufficient physical capital is accumulated. Other results are that some economies may reach a steady state of physical capital before a take-off is possible. This is especially likely for economies in which agents have low savings propensities. Such economies remain stuck in a no-growth equilibrium forever. Economies that do grow may experience endogenous cycles if the return to investment in human capital is sufficiently increasing in the level of physical capital.     

“Good Cause Beliefs” in an “At-Will World”? A Focused Investigation of Psychological Versus Legal Contracts

This study assesses the psychological contracts of a group of at-will employees and compares their relevant psychological contract beliefs with the terms of the controlling legal employment contract. In addition, we test specific hypotheses regarding the relationship between employers formal job security policy (employment at-will vs. good cause protection, and employee personal characteristics; equity sensitivity, organizational tenure) to 2 focal psychological contract beliefs (the employers obligation to have a good reason to discharge the employee, and the employees reciprocal obligation to have a good reason to leave his/her employer). These issues are investigated using survey data sampled from 15 diverse U.S. organizations, and independently collected information regarding organizations job security policies. The results provide evidence of a widely shared psychological contract belief that, despite explicit at-will policies, U.S. employers are highly obligated to have a good reason to discharge employees. Further, personal characteristics are more strongly related to the focal psychological contract beliefs than employer job security policies. The theoretical contribution of the study and its practical implications are discussed.     

Die Charakterisierung der Normalverteilung nach Gauß

A proof is offered for the best possible version of the following Gauss type characterization of normality: LetF () be a family of distribution functions with translation parameter such thatF (0) has a densityf with certain regularity properties, and letM{1, 2, ...}. If the mean of every sample of any sizemM is a maximum likelihood estimate of , thenF (0) is normal with zero expectation. While in the best prior version of this theorem,f satisfies a continuity assumption andM={2, 3}, here no regularity condition is needed, andM can be any of the sets {3}, {4}, ....     

The transition from central planning to a market economy: A computable general equilibrium model

This paper develops a computable general equilibrium (CGE) model of the transition from a central planned economy to a market economy. The model is an extension of Wellisz and Findlay's (1986) model of the Soviet second economy. By distinguishing alternative assumptions about the disposition of the government budget, two model variants — the activist and non-activist — are analyzed. Equilibria of these model variants are computed for various parameter specifications of the Kantorovich ray, which represents the stringency of central planners' direction of the economy. The paper shows that increasing efficiency of the private sector, while it reduces the size of government subsidies to the state sector, does not necessarily increase the net government budget.     

Effect of outliers on the estimation of parameters

Summary The estimation of parameter in the type of distributionf(x)=b x ^{–1 /b} exp (–x ^b (/b),x>0, is considered, when several outliers of the type , ,r=1,2, ...,k, are present in the data. The estimates of as well as of 's are put in the closed form. Special cases, Weibull, Gamma and Exponential are considered for the case of single outlier. Actual estimates are calculated from the generated samples of size 2 and 3 for the Weibull and Exponential.     

Economic planning and information

Conclusions The central arguments for national planning put forward during the early part of this century were decisively refuted by Mises and Hayek during the 1920s and 30s (see Hayek, 1948). General equilibrium theory of the 1960s provides no more adequate justification for the version of indicative planning proposed in this article. It is disappointing to see that no account has been taken of the important recent developments in economic theory and analysis which provide a more realistic basis on which to compare the private market and government agencies.There is no doubt that the country's future growth and development depend upon identifying more profitable investiment opportunities in the British economy (p. 140). There is equally no doubt that an infinite number of such opportunities exist. But how to identify them? Regrettably, Paul Hare does not tell us.     

The large-sample power of the 195-1195-1195-1test for multidimensional contingency tables

Summary The asymptotic power of the frequency ² test depends on a noncentrality parameter, ,Mitra [1958] offered a general expression for , which is rather difficult to apply. This work provides simplified formulae for in various models associated with multidimensional contingency tables.     

Una classe di funzioni monotone generalizzate

Si considera la classe delle funzioni realiF(x,y) definite inS×S, conSR ^N , che soddisfano per ognix,yS la condizione di monotoniaF(x,y)+F(y,x)0. Indebolendo la precedente disuguaglianza si introducono classi di funzioni monotone generalizzate e, supponendo soddisfatta una opportuna condizione di omogeneità, si caratterizzano tali funzioni in base alla struttura del segno delle funzioni _{x, v} (t, s) = F(x + tv, x + sv), x S, v R ^N \{0}. Infine dopo aver definite le funzioni F-differenziabili, si introducono classi di funzioni conversse generalizzate, rispetto ad F, e si studiano i collegamenti tra queste classi e la monotonia generalizzata diF.

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Summary We consider the class of real valued functionF(x,y) defined inS×S, withSR ^N , satisfying x,yS the monotone conditionF(x,y)+F(y,x)0. Weakening the previous inequality we introduce the class of quasi-monotone, pseudo-monotone and strictly pseudo-monotone functions. Under a suitable assumption of homogeneity we characterize the generalized monotone functions studying the sign structure of the functions _{x, v} (t, s) = F(x + tv, x + sv), x S, v R ^N \{0}.Finally by means of the notion ofF-differentiability we introduce new classes of generalized convex functions (with respect toF) and we study the relationship between these classes and the generalized monotonicity ofF.

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Questa ricerca è stata parzialmente finanziata dal Ministero per l'Università e la Ricerca Scientifica.     

Multiple patterns in the dynamics of a stock market model

We study a non-linear model of the interactions between stock market prices and the level of assets owned by investment funds. The model dynamics is described, in continuous time, by a smooth vector field in the plane, which presents, under suitable hypotheses, a unique equilibrium point.Our analisis of the system flow is qualitative and focuses on detecting endogenous fluctuations of the state variables, i.e. on checking existence and number of limit cycles.We prove that several, and quite different, dynamical patterns can occur, even in cases where the system isoclines assume that most simple geometrical forms.It is shown, in particular, that the equilibrium point can undergo either a sub-critical or a super-critical Hopf-bifurcation whenever two economically meaningful exogenous parameters are made to cross a given set of critical values. Hence, in the subcritical case, as a trapping region exists, at least two limit cycles appear.Next, we give analytical examples of model-consistent vector fields which present a multiplicity of fluctuating trends, and prove the apparently surprising result that the number of limit cycles can be as large as one wants, provided a specific isocline assumes a cubic shape.Both authors are members of the Gruppo Nazionale per l'Analisi Funzionale e le sue Applicazioni-G.N.A.F.A. of the Italian Council of Researches-CN.R.The present paper refers to the activities of the National M.U.R.S.T. Group Dinamiche Non Lineari ed Applicazioni alle Scienze Economiche e Sociali.     

Trade liberalisation and endogenous growth: Some evidence for Turkey

This paper examines the impact of trade liberalisation on the long-run economic development as measured by the real GDP per capita in Turkey. Based on the endogenous growth theory, we employ bivariate and multivariate cointegration analyses to test the long-run relationship among the relevant variables. Results for Turkey suggest a stable, joint long-run relationship among real GDP per capita, an index of trade liberalisation, human and physical capital in accordance with the endogenous growth theory. Statistically significant error-correction terms provide further evidence that those variables are indeed cointegrated. This also implies causal effects.     

A note on optimum spacing of observations from a continuous time simple Markov process

Summary Assume thatX() is a continuous time simple Markov process with a parameter . The problem is to choose observation points ₀ < ₁ <...<_T which provide with the maximum possible information on . Suppose that the observation points are equally spaced, that is, fort=1, ...,T, T, ;_t–_t–1 is constant. Then the optimum value fors is obtained.     

An identity concerning a Wishart matrix

Summary LetS be ap×p Wishart matrix with parametersn and . For a rational number =r/s withr ands integers ands positive, letS denote a positive definite matrix such that (S ) ^s =S ^r . Using a decision theoretic argument, we prove thatE[(trS)² trS ]=(np+2+2)E[trS trS ] when =I andnp+2+2 is positive.     

Eine simultane Charakterisierung der geometrischen Verteilung und der logistischen Verteilung

Summary LetE denote the generating function of a non-degenerate probability distribution on the positive integers, letF be a non-degenerate distribution function, and let be a real valued function on the interval (0, 1]. In the present paper the solutions (E, F, ) of the functional equationE(F(x)/E()=F(x+()), –<x<+, (0, 1] are given. It is shown that ifF is symmetric about zero,E andF belong to a solution of the functional equation if and only ifF is a logistic distribution andE is the generating function of a geometric distribution.     

Law without justice: The dilemmas of formalization and fairness in the legalistic organization

There is growing evidence of a litigation mentality rampant in organizations, which has created a legalistic mindset in many managers. Increasingly, managerial decisions are becoming dominated by a concern for what is legally defensible at the expense of broader social considerations such as justice and fairness. The papers in this special issue explore how this legalistic mindset has created new organizational and social dilemmas, and situations of law whithout justice.     

Vergleich des verallgemeinerten nichtzentralent-Tests mit dem Binomialtest

Zusammenfassung Es sei {F _,(x); –<<, >0} mitF _,(x)=F((x–)/)–F(x) eine standardisierte Verteilungsfunktion — die Familie der zulässigen Verteilungsfunktionen. Der (früher eingeführte) verallgemeinerte nichtzentralet-Test für die Hypothese {PP ₀} mitP:=F _,(x ₀) gegen die Alternative {P>P ₀} zum Niveau wird mit dem entsprechenden nichtparametrischen Test (Test für die Hypothese {pP ₀} über den Parameterp einer Binomialverteilung gegen die Alternative {p>P ₀}) verglichen. Für dent-Test wird die relative asymptotische Effizienz bestimmt.Beide Tests lassen sich als Tests für das zur WahrscheinlichkeitP ₀ gehörende Quantil einer Verteilungsfunktion interpretieren. Der klassische zentrale Student-Test ergibt sich als Spezialfall (F(x)=(x),P ₀=0,5).

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Summary Let {F _,(x);–<<, >0} withF _,(x ₀):=F((x–)/–F(x) a standarized distribution function — the family of admissible distribution functions. The (earlier introduced) generalized noncentralt-test for the hypothesis {PP ₀} withP:=F _,(x ₀) against the alternative {P>P ₀} at level of significance is compared with the corresponding nonparametric test (Binomial test). The relative asymptotic efficiency of thet-test is determined. Both kinds of tests can be interpreted as quantiltests. In caseF(x)=(x),P ₀=0,5 one gets the classical central Student-test.

     

Wrapped distributions and measurement errors

Summary For a random variableX and >0 letU n (X)–X, wheren (x)=nZ iffx(n–/2,n+/2]. Random variables of this type are important in the theory of measurement errors. We derive formulas for the distribution ofU and apply them to the case XN(,²). General conditions for the unimodality ofU are given. The correlation of the measurement errorsX–E (X) andU (X) is seen to beO (^j) withj depending on the smoothness and asymptotic behavior of the density ofX. This gives a precise sense to the assertion that scale errors upwards and downwards are averagely well-balanced. In the normal case the density ofU is shown to be constant up to , as 0.