Toepassing der waarschijnlijkheidsrekening op enkele verkeersproblemen in de automatische telefonie

An investigation is made about the probabilities of loss and delay in automatic telephone traffic, using the method of the statistical equilibrium.
The validity of several formulae found by Erlang, is discussed in connection with the fundamental formula of Poisson.     

De bewerking van de resultaten van veldproeven door herleiding van de opbrengstcijfers in beide richtingen van het proefveld

Summary  (The treatment of the results of field experiments by reducing the yields in two directions)
Ir J. J. Dijkveld Stol has shown that good results have been obtained by reducing the yields of field experiments both in columns and in rows.
The mathematical foundation of this method is discussed in the preceding article and it is shown, that the method gives good results if the same supposition may be made as necessary for the application of the methods of Fisher, Knut Vik and the method of the differences.
The variance of Dijkveld Stol's method is identical with Fisher's error variance.     

Dimensionering van homogeniseringsinstallaties

Designing of homogenizing equipment
The spread in quality in a large stream of granular material can be sufficiently reduced only by homogenization in mixing heaps and bunker installations. In this treatment each unit of consumption is composed of portions which, at given intervals, are taken from the stream.
The paper indicates how to choose the number and size of the portions and the intervals between them in order to achieve the required reduction in spread at minimum costs.
This determination, elucidated by means of an example, is based on the correlo-gram of the stream referred to thin slices.     

De bewerking van veldproeven volgens de methode van Knut Vik

Summary  (The treatment of field experiments by Knut Vik's method).
Agriculturists and statisticians have studied the problem, how to free the yields in a field experiment from the inequality of the soil. The method of the analysis of variance, due to the English statistician R. A. Fisher has taken an important place in the study of field experiments, so that other methods fell in the background.
The Norwegian agriculturist Knut Vik has suggested a method, which leads to good results without complicated calculations and without the knowledge of a great part of the mathematical statistics.
The mathematical foundation of this method is discussed in this article, which concludes, that the method of Knut Vik is of great importance for agriculturists, who don't want to perform intricate calculations.     

De oplossing van een kwaliteitsprobleem door het gebruik van proefschema's

Samenvatting  Het artikel geeft een beschrijving van de strategie en de methoden, die worden gebruikt voor het zoeken naar de oorzaak van een kwaliteitsvermindering bij dubbelspiralen voor gloeilampen. Er wordt niet alleen aandacht besteed aan de beschrijving en motivering van de gekozen proefschema's maar ook aan de praktische uitvoering van de experimenten. Het fabricage-proces is nl. dermate gecompliceerd dat niet kon worden volstaan met de instructie de experimenten in aselecte volgorde uit te voeren.
Het gehele onderzoek wordt uitqevoerd aan de hand van een drietal proefschema's. De keuze van het tweede en derde proefschema volgt logisch uit de uitkomsten van de voorafgaande proef. Na vol-tooiing van de derde proef is ondubbelzinnig aangetoond dat de belangrijkste oorzaak van de kwaliteitsvermindering is gevonden.     

Een steekproef ter vaststelling van de verdeling van de hoenderstapel

A sample estimate of the poultry distribution
In 1954 a sample survey was carried out of the returns of the agricultural census, May 1954, in order to establish the distribution of the number of holdings and the number of poultry, by size-group of arable land and by size-group of number of poultry. A simple 10 per cent, sample was planned and the expected variances of the numbers of poultry in each size-group were estimated beforehand. The method of estimation is indicated in this paper. This resulted in comparatively high relative errors in the size-groups above 500 hens and also in the size-groups of arable land. Therefore holdings with 500 hens and over were enumerated completely. Some tests were performed with the sample results and finally the efficiency of the stratification is discussed.     

Assortimentsbepaling van seizoenprodukten

This paper deals with the analysis of a problem often met when determining purchasing policies. From a number of different kinds of goods, which are to be bought, the total quantity is restricted by storing capacity or financial limits. The problem "how much of each kind will be bought" is solved for a discrete as well as for a continuous distribution of demand for the various goods.     

Het oordeel van een bedrijfsleider over de toepassing van de statistiek in het bedrijf

A manager's view on the application of statistics in the concern.
To be able to judge of the correct dosing of statistical methods in his concern a manager should discriminate between incidental research and systemetical application of statistics. A sound job limitation and good information are indispensable to the success of a statistical check system.
The cost of the introduction of statistical check methods into a concern with a variated manufacturing programme in the field of electrical engineering (350 people) was estimated to be Djls 18,000 in one year. In the next year more than this amount will be earned back through the savings and the improvements obtained.     

Constructie van kansellipsen in een correlatiediagram

Summary  (Construction of chance ellipses in a correlation diagram).
Chance ellipses in a correlation diagram are calculated from the formula of the normal correlation surface (the chance ellips P contains the area of the correlation diagram, where P% of the observations are found). The construction of these ellipses is explicated. A table with factors to construct the ellipses for different values of P is added.     

Bepaling van stuwende en verzorgende bedrijfstakken door middel van statistische methoden

Determination of basic and non-basic enterprises by means of statistical methods.
In this article a sketch is given of the various methods used to obtain a clear insight into the meaning of the non-basic enterprises and the enterprises which because of their basic character belong to the factors determining the development of the population. Special attention has been paid to the method which puts the whole problem of the definition of basic and non-basic industries in the framework of a system of equations. This system has been built up from regional social accounts that have been developed for Amsterdam.     

Superpositie van twee frequentieverdelingen

Summary  (Superposition of two frequency distributions)
Notation:
n: number of observations
M: arithmetic mean
: standard deviation
μ_r: r^th moment coefficient
β₁: coefficient of skewness
β₂: coefficient of kurtosis.
The suffixes a and b apply to the component distributions. The suffix t applies to the resulting distributions.

The problem: Given the first r moments of two frequency distributions (to begin with μ₀). Find the first r moments of the distribution resulting from superposition of the two components ( r ≥ 5 ).
Formulae [1]. … [ 5 ] (§ 3 ) give the results in their most general form up to μ₄.
Some special cases are treated in § 4, and eight different cases of superposition of two normal distributions in § 5.
In § 6 some remarks are made about the reverse situation, i.e. the splitting into two normal components of a combined frequency distribution.     

Biologische waardebepalingen van geneesmiddelen

The aim of standardization is to make sure that different batches of a drug do not vary in their potency. With most drugs this can be done by chemical methods, for a certain number of drugs however biological methods are still necessary. The best procedure to standardize a drug is to use a standard preparation. In this lecture it is discussed which demands must be made upon standard and the criterion. The measurement of the pyrogenic activity of drugs is discussed as an example.     

Optimale rantsoenering van aardolie en aardolieprodukten in Nederland; een toepassing van input-outputanalyse en lineaire programmering

Samenvatting Bij een invoerrestrictie van ruwe olie ontstaat het probleem van de optimale verdeling van de olie over de verschillende bedrijfstakken. Met behulp van input-outputanalyse kan dit probleem worden getransformeerd in een lineair-prograrnmeringsvraagstuk. In het navolgende artikel worden een aantal oplossingen gepresenteerd die men verkrijgt bij verschillende veronderstellingen omtrent bezuinigingsmogelijkheden, verbruiksminima enz.     

De betrouwbaarheid van controleurs

Summary  (The reliability of 100% inspection).
The article of Mr, Enters on The reliability of 100% inspection in the first issue of Statistica is critizised.
The criterion of goodness of control as the sum of the coefficients of correlation between the measurements of the individual inspectors and each of their colleagues does not agree with the everyday use of that criterion, i.e. the correlation between the observed' and the real diameters etc. Nor is this criterion identical with the Spearman criterion of saturation coefficients.
Some suggestions are given for solution of the problem, e.g. psychotechnical testing the inspectors, analysis of the frequency curves of their measurements and computation of the coefficients of correlation between the measurements of each inspector and the corresponding average measurements of all inspectors.