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.     

Het voorspellen van levertijden uit gegevens over de voort-gang van een project

Estimation of dates of delivery by extrapolation of progress-data for a project.
The problem can be put in mathematical form with the aid of some assumptions with regard to the occurrence of interruptions.
The progress of the project is supposed to be interrupted by time-intervals during which progress is fully stopped. These intervals start at irregularly distributed moments and have a variable size. The points on the time axis corresponding with the moments of stagnation will show a constant average density, if a constant average production capacity or development capacity is available. This means that the results are valid only if no alterations are made which influence the general progress of the project involved.
The application of probability theory to problems connected with promises of delivery may, in general, look unacceptable.
Many projects, however, have an experimental character and unforeseen technical and organisational troubles are unavoidable.
In such cases the theory makes it possible to obtain a maximum amount of information contained in the progress-data and may help management to make the best decisions.     

De Computer: Werkwijze en toepassingsmogelijkheden van elektronische rekenmachines

Since world-war II, there has been an enormous development in the field of the electronic data processing equipment.
This rapid development was on one side due to the boom which followed the war, on the other hand the armaments-race contributed considerably to a further increase of the research in this sector.
In the years 1948–50 it became clear that this equipment could also be of great advantage in other areas than scientific, such as business administration, automatic translation, information retrieval and production control. These applications, however, made other demands on the computer. A greater and faster memory and more speed in input and output of data were necessary. The research in the last few years is therefore mainly concentrated on these problems.
The computers, as they are now available, consist of 5 units: input device, calculating-unit, storage, control unit and output device. The processing is controlled by means of a program, which consists of a number of instructions, prescribing in detail the operations to be performed by the machine.
It will be clear that the use of this equipment requires a careful study beforehand, whilst also the implications on staff and organisation must be considered.     

Een systeem van kostenbeheersende productieplanning

In this paper a system of cost-controlled production planning is described. This system considers all kinds of costs associated with a production in phases (e.g. production of units, production of subassemblies, assembly) which may be affected by the planning, such as set-up costs, costs of transport, control, inventories, capacity and changes in capacity.
The mathematical model leads to a linear or mixed discrete-linear programming problem whose solution gives for each time period considered the size of the capacities which should be used and of the series of different products which should be produced. Practical recommendations are given for obtaining a sufficiently satisfying solution.     

Eenvoudige mathode voor het interpreteeren van statistisch contröle-materiaal

A simplified method for the working out of statistical control data by means of a suitable abacus is described and explained. A practical example for a population corresponding to the Normal (Gaussian) Curve is given. This method can also be applied to Frequency Distributions not obeying the Law of Gauss, provided they can be represented by a known mathematical function.
A simplified method for the compilation of statistical data concerning weights by means of a balance provided with numerators, is described.
The possibility of the application of a system of numerators to automatic dosing machines is discussed, by means of which control, based on random sampling, could be replaced by weighing dosages individually.     

Aantekeningen bij de herziening van de methodiek der prijsindexcijfers van het levensonderhoud

Momentarily (fall 196o) the Netherlands Central Bureau of Statistics is revising its price indexnumbers of family living. Some features of this revision are summarized below.
The old series is based on an expenditure pattern of 1951, whereas the new series will be calculated according to an expenditure pattern of 1959/'60. The latter data will be derived from a budget survey held among 250 households of manual and clerical workers consisting of 4 persons and grossing between four and eight thousand guilders a year (para. 6). The period covered was April 1959 till April i960.
The author indicates the way in which the varieties of the budget items to be covered by the monthly price surveys are chosen (para. 7). He discusses the principles and results of determining the number of price quotations (para. 8).
The choice of the municipalities in which price data will be collected is explained. An outline is given of the organisation of the new surveys apparatus (para. 14).     

Toespraak door de directeur van de Stichting "Kwaliteitsdienst voor de Industrie"

Adress of the Director of the Foundation Industrial Quality Service.
The increasing of productivity also has an important qualitative aspect, To promote the qualitative increase of productivity the "Kwaliteitsdienst voor de Industrie" (Industrial Quality Service) wants to organize courses through which the statistical quality control methods can for each separate branch of industry be made available to those who are able to apply these methods, but who cannot spare the time and the energy required to take fully note of the mathematical and statistical backgrounds.     

Afleiding van kwartaalcijfers uit jaartotalen

Summary  Quarterly figures may be required when only a sequence of annual totals is available. This article presents two reasonable methods for "interpolating" quarterly figures by means of appropriate minimizing procedures.
The first method relates to minimizing the sum of squared second differences of the quarterly figures, the other one is a linear programming procedure which refers to the absolute second differences. Both methods are illustrated by a numerical example, the first one giving somewhat better results.     

De omvang van de steekproef bij een enkelvoudig steekproefsysteem

Summary  (Sample size for a single sampling scheme).
The operating characteristic of a sampling scheme may be specified by the producers 1 in 20 risk point ( p ₁), at which the probability of rejecting a batch is 0.05, and the consumers 1 in 20 risk point ( p ₂) at which the probability of accepting a batch of that quality is also 0.05.
A nomogram is given (fig. 2) to determine for single sampling schemes and for given values of p₁ and p ₂ the necessary sample size ( n ) and the allowable number of defectives in the sample ( c ).
The nomogram may reversedly be used to determine the producers and consumers 1 in 20 risk points for a given single sampling scheme.
The curves in this nomogram were computed from a table of percentage points of the χ² distribution. For v > 30 Wilson and Hilferty's approximation to the χ² distribution was used.     

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.     

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.     

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.     

Tabellen en nomogrammen voor het onderscheidingsver-mogen van de 5% en 10%-F-toets voor het gebruik bij de gewarde blokkenproef

Tables and graphs of the power of 5% and 10%-F-tests for use in randomized block experiments.
As randomized block experiments occur so often in agricultural and other research, it was thought worth while to adapt existing tables of the power of 5% F-tests for this special case: The author hopes that in this way the design of experiments in terms of power will be facilitated. Moreover new tables were computed for the power of 10%-F-tests.
The tables have been summarized in graphs that greatly facilitate their use. Illustrations are given in practical problems.     

Over de spreiding bij het droge-stofonderzoek van brood

The accuracy of the determination of the amount of solids in bread.
Of a loaf with a nominal weight of 800 grams only about 480 grams remains after complete drying. This so-called 'amount of solids in bread' is regularly checked by samples. From a batch of loaves a group of at least 5. but usually more, are taken at random and weighed. From this group one is selected with a weight as nearly as possible equalling the average weight of the whole group; for two slices of this sample loaf the decrease in weight upon drying is determined in the laboratory, and is considered as representative for the entire batch.
The accuracy of these determinations is analysed on the basis of 35 samples which were investigated in 3 different laboratories. The standard error is estimated at 5 grams per loaf. The influence of various factors, such as the method of sampling which may be altered in many ways, is briefly considered, while in a final section the results obtained are discussed from a practical point of view.     

Produktiviteitsverhoging op grote schaal: Maatnormalisatie van kleding

The article contains a short review of a campaign, undertaken in Holland during the last 12 years to arrive at standardized sizes for women's and men's clothing. The first campaign was undertaken by a department store, the second one by the clothing industry.
The operational value of a sizing system depends on the value of three parameters which are not, of course, independent of each other: coverage of the system, number of sizes and average cost of alterations.
The basis of the standardization is furnished by measuring a sample of the population of customers and by measuring the fitting-tolerances of clothing.
The proposed sizing systems are:
a. Ladies' dresses — a two-dimensional system based on waist girth and length of back, containing 14 sizes and giving a coverage of 90%.
b. Men's suits — a system with a variable number of dimensions (2 to 4). The identification dimensions are waist girth, length of leg, hip girth and inclination of shoulder. The proposed system gives a coverage of 90% with 34 sizes. Both systems have been experimentally verified.
Stress is laid on the necessity of an international sizing standardization.     

Produktiviteitsverhoging bij accountantscontrole door toepassing van gelaagde steekproeven

The auditor's productivity: application of stratified sampling to an auditing problem.
In this paper it is shown that the use of stratified sampling can lead to a considerable saving of costs in auditing operations and thus increases the auditor's productivity.
The sampling method to be described will render it possible to say that the total value of the transactions will not differ more than a fraction φ, given in advance, from the correct total value, apart from a probability not surpassing a preassigned level e, on condition that a certain acceptance criterion is fulfilled. Taking into account the auditing costs, the author gives an optimal sampling design and calculates the savings obtained.
Finally the theoretical results are applied to a population of clerical transactions, with an exponential and a logarithmico-normal distribution respectively.     

Een opmerking over het aanpassen van functies aan een groot aantal waarnemingsuitkomsten

Note on the fitting of a function to a large number of observations.
The paper deals with various ways in which a set of functions may be chosen to describe a given body of observations, the parameters determining the function being determined by the data.
The special case when the functions of the set are given in the form of a table or a graph is emphasized.