Assurance Of Accuracy Research Articles

Special aspects of the assurance of accuracy in measurements of coating thicknesses

Factors underlying the difficulty of assuring high accuracy in measurements of the thickness of coatings are investigated, specifically the enormous diversity of coating and base materials with different physical properties, the large number of influencing variables, lack of unification in the interpretation of the concept of “coating thickness,” insufficient localization of measurements on the part of present-day thicknesses gauges, the broad range measurements, and small absolute errors.

Assurance of accuracy in determinations of contents of micro components in samples of very pure substances and in environmental specimens

We propose an approach allowing us to use preliminary enrichment (concentration) in accordance with the characteristic features of the method for taking into account the resulting systematic error based on the relationship between the systematic error of the analysis results and the determined content. This allows us to avoid a number of difficulties specific to quantitative determination of very low contents with substantial improvement in the accuracy of the final analysis result.

Predicting tree frequencies from pollen frequency: an attempt to validate the R value method

SUMMARYPollen‐tree correction factors are presented using regression analysis of pre‐settlement tree and pollen frequency data from 32 small lakes (1–10 ha) in Wisconsin. Regression results using vegetation samples from various sized areas around each lake for Fagus grandifolia (Ehrh.) and Tsuga canadensis (Carr.), are consistent with my initial design of using vegetation data for the single township in which a lake was found to compute the regression results. Pollen‐tree correction factors from pre‐settlement and modern data were compared for all major pollen types. Notable differences were found between pre‐settlement data and modern data sets for Wisconsin in Betula spp, T. canadensis, and Quercus spp. Little difference was observed in the fit of the regressions for these data sets. Estimations of pre‐settlement relative tree frequencies, derived from the application of modern correction factors on pre‐settlement pollen frequencies, were compared to measurements of pre‐settlement vegetation. The reconstruction of pre‐settlement vegetation was incongruous with measurements of pre‐settlement tree frequencies. It is unclear, given minor differences in the data sources for modern and pre‐settlement data, whether the observed differences in regression results are artifacts of the data sets, or reflect differences in pollen‐tree representation between the two time periods sampled. Regardless, the error associated with prediction of tree frequencies from pollen frequencies is shown here to preclude any assurance of accuracy with normal pollen count levels.

Interactive design based on the p-version of the finite element method

A case study, concerned with shape optimization of a plane elastic body, is presented. The study focuses on the assurance of reliability and accuracy of computed data on which design decisions are based. The design procedure is interactive in the sense that the designer chooses the design parameters on the basis of information generated in the analysis cycle.

Software for Reliability Testing of Computer Peripherals: A Case History

This article addresses: 1) the problem of inadequate software for the reliability testing of computer peripherals, and 2) the development and use of a software package specifically designed for reliability testing of disk drive peripherals. The software package enables one to carry out controlled reliability testing of disk drive peripherals. Necessary data for statistical calculation are available when needed and in the detail required. Non-drive errors can be isolated and not allowed to distort test results. The soundness of data collected allows for long-term testing under changing conditions to proceed with assurance of accuracy. Product reliability and thereby customer satisfaction can be more fully assured. The creation of the software also provided an outline of a sound methodology for future reliability software development. This methodology has continued to be employed within Intel and at a number of the vendors supplying Intel with disk drive peripherals.

Simple Sextant Calibration

When the scale readings of a sextant are suspected of error, or if an assurance of scale accuracy is needed, optical equipment for establishing angles is rarely available. Comparison with another sextant is possible, but if the arc between two stars were measured by bringing them into coincidence this could be compared with the calculated angular distance. To calculate the distance from a spherical triangle, knowing the stars' declinations and right ascensions, would be laborious and the refraction corrections would be difficult to apply—as they were in the old lunar distance methods. It is far simpler, in the northern hemisphere, to take Polaris as one of the two stars. If the other is within an hour of its meridian passage, so that the measured arc is approximately vertical, the usual corrections for refraction are sufficient. Also the calculated angular distance will then be simply 90° – δ, where δ is the declination of the star selected. This calculated distance is therefore subject to two corrections:(i) refraction corrections for both stars,(ii) a correction for Polaris not being exactly at the pole.

Excerpts from AEC Statement on Nuclear Blast Effects

AbstractThe following estimates of the possible effects of nuclear detonations of various megaton yields are subject to many uncertainties. It is impossible to predict with any assurance of accuracy the effects of actual detonations of very high yields, particularly at high altitude.

ECONOMICS OF COASTAL STRUCTURES

The engineer is constantly called upon to make an economic analysis of proposed engineering works. His analysis is just as trustworthy as his base information. In some cases experience and knowledge are so complete that an estimate can be accepted with assurance of great accuracy. The purpose of this paper is to discuss some of the factors involved in making an economic analysis of coastal structures.

Some Suggestions on the history of Potato Virus X.

Summary Although virus X is carried by the potato almost without symptoms and was first discovered only twenty-two years ago when it was already nearly ubiquitous, its history outside South America can be traced over the centuries with some assurance of accuracy. Potatoes of diverse varieties were brought to Basutoland and Tristan da Cunha in the last century and since grown in isolation. They are free from virus X which, because the virus is not thrown off by clones which have become infected, indicates a high general level of health at that time. The change which has come about elsewhere since then is not merely fortuitous. A hundred years ago varieties were innumerable and mostly short-lived; and between changes of variety there was normally little chance for the virus to accumulate. Nowadays the varieties which are extensively cultivated are relatively few and mostly long-lived. With their longevity has come the chance for the virus to accumulate; and the accumulation has been helped by a seed industry which controls leaf-roll and severe mosaic, thus obviating the need for changing varieties, but not virus X except in its more severe strains. American varieties were apparently infected early: too early for the history of the attack to be traced. British varieties seem to have been attacked later, and the evidence of ‘Up-to-Date’, with a hint of confirmation from ‘Champion’, is that infection was scarce until about the second decade of this century. Losses from virus X, conservatively put at 800,000,000 bushels a year for the world over, are both an indictment of the organization of the seed industry and a warning against the danger of abandoning varietal abundance and novelty in crops which are propagated by vegetative means.

Pitfalls to be Avoided in the Roentgen Diagnosis of Intracranial Disease

Too often, in our enthusiasm for the positive side of diagnosis, we are apt to forget the equally important but less spectacular negative side, and because of this we may be led into considerable error. Hence, it may not be amiss to consider briefly some of the pitfalls of cranial diagnosis into which one can easily fall. The first and most frequent “pitfall” is to attempt to draw conclusions from an inadequate set of films, or from those which are the result of poor technic. We are all familiar with the fact that in about 50 to 60 per cent of adult skulls the pineal body will be calcified sufficiently to cast a shadow on the film, and most of us are aware of the methods in use for measuring its relative position. These methods are all based on proportional measurements, either mathematical or mechanical, and with either method we allow ourselves an arbitrary normal zone. If the pineal shadow falls within this normal zone, we usually feel a sense of relief and conclude that the gland is not displaced; if it is slightly out of this zone, we consider it displaced. In the vast majority of cases, these conclusions will be correct, but we cannot accept such a finding without careful consideration of each case as an entity. The reason for this lies in the fact that the pineal body may be shifted from one part of the normal zone to another without the measurements revealing such a shift. This normal zone is really too large for extreme accuracy; therefore, we must be careful to evaluate the patient as a whole before stating definitely that the pineal body is or is not displaced. Again, an innocuous anatomical variation may locate the pineal gland slightly outside the normal zone. This discussion should not lead one to conclude that the use of our present schemes for pineal measurement must be abandoned. They are the best methods we have so far been able to devise and should by all means be used, but used with the full knowledge that they are not infallible and that we cannot accept the results with as complete assurance of accuracy as we can the reading of a thermometer. The discovery of a lateral pineal shift offers no problem in good films taken either anteroposteriorly or postero-anteriorly. Another easy diagnostic pitfall is the misinterpretation of an anomalous configuration and distribution of circulatory channels. Not infrequently we will find the diploic venous channels to be larger than usual. This anomaly may be confined to the frontal, parietal, or occipital group of veins, or may involve all of them. In any case, the channels may all be large and tortuous, or some may be large and others small. When this problem confronts us, we must carefully compare both sides of the head since the condition is usually bilateral. If there seem to be more and larger venous channels on one side than on the other, it is probably of no more than passing interest, provided we are sure that the channels are venous.

Statistics in Social Insurance

In social insurance statistics have two broad and closely related functions. They are, using the expression in its broadest sense to include the entire purview of management, essential as administrative tools. Also and at the same time they provide a convenient and convincing method of education. For the administrative use executives have often no worthwhile substitute and as time goes on refinement of statistical method and the inevitable competitive pressure of other demands on public funds will both permit and encourage them to lean more and more on control through statistics. The educative use of statistics is not limited to indicating the importance of passing new laws and setting up new systems. Almost the contrary. The highest standards of public service imply not only routine administration but continuous consistent reexamination of a system in the light of its postulates. Because of the scope of this paper and because in practice they merge and interact, the educational and administrative uses of social insurance statistics in the following discussion will generally be considered together. Workmen's Compensation Statistics-We have in this country our longest experience and-in terms of our opportunities-our greatest statistical failures in the field of workmen's compensation. Workmen's compensation statistics, for those who look forward to other social insurances, are at once a warning and a consolation. They illustrate in broad terms what we ought to avoid. They hearten us by showing how much can be done under the inevitable handicaps of federated government. The administrative uses of workmen's compensation statistics are principally: to prevent or minimize industrial injuries, to secure efficient treatment of claims, to assure speed and certainty of compensation payments including assurance of accuracy of rates and of reserves. In a going system the principal sources of statistics are naturally found within the system. Workmen 's compensation (except for longshoremen and harbor workers) is in this country almost exclusively a matter of state concern, and the standards of statistical information in this field vary widely. State labor departments and accident boards provide information on such matters as accident numbers and rates, delay in payments, 221

CANCER IN HONGKONG, SHANGHAI AND BERMUDA

To the Editor: —Through the kindness of the Statistical Division, Army Medical Library, Washington, D. C., there have recently come to me some rather interesting cancer data for the European and Chinese population of Hongkong, the European population of Shanghai and the general population (mostly mixed blood negro) of Bermuda, which may be interesting to the medical profession and to those concerned with cancer investigations otherwise. The Hongkong data are for the period 1911-1920. It is obvious that the rates shown for certain years, at least, are of doubtful value on account of the uncertainty as regards the correct number of foreign residents since the war. Previous to 1915, however, the data may be accepted with assurance of accuracy, and likewise for the last three years. In view of the fact that the actual mortality is very small, it should not be difficult to subject the returns to a qualified

Romanes on Weismann

DR. ROMANES is a most competent hurler of hard words, and in this volume is concerned at least as much to convince the reader that Weismann is an uncertain guide as to be to him himself a certain guide. In the preface he states his intention to publish his criticisms “in separate form and in comparatively small editions, so that further chapters may be added with as much celerity as Prof. Weismann may hereafter produce his successive works.” In the text, writing of the relations between the views of Galton and Weismann, he talks of those immense reaches of deductive speculation, which, in his opinion, merely “disfigure the republication of stirp under the name of germ-plasm” (!) The mention of certain occurrences which are believed in by Dr. Romanes, but the admission of which he considers illogical on the part of Weismann, “seemed attributable to mere carelessness on the part of their author.” Another consideration is “made by Weismann for the sole purpose of saving as much as he can of his previous theory of variation.” Another is “an obvious equivoque.” The mechanism of heredity is planned out (in Weismann's latest volume) “in such minuteness of detail and assurance of accuracy that one is reminded of that which is given by Dante of the topography of the Inferno.” An Examination of Weismannism. By G. J. Romanes (London: Longmans, Green, and Co., 1893.)