Sham accuracy

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In statistics and natural sciences, sham accuracy or pseudo-accuracy is understood to mean the recording or presentation of data or results with a resolution that the underlying measurements or data do not provide at all.

Causes and consequences

Oil consumption per day recorded with sham accuracy by continent

Causes of apparent accuracy can be:

  • The significant digits are not properly taken into account; This happens most often when two measured values ​​are offset against each other that have different accuracies. In order to determine the result, the result must be rounded in such a way that the accuracy of the less precise value is used, otherwise the result suggests an accuracy that it cannot have. Example: if the two measured values ​​24.76 ° C and 34.1234 ° C are offset against each other, e.g. B. by addition, the end result must not be 58.8834 ° C, but only 58.88 ° C. The reason for this is of a purely logical nature and not an arbitrary determination. There are always measurement inaccuracies , and their order of magnitude is reflected in the recorded measured value (if measured correctly).
  • Results calculated on the computer are often adopted 1: 1 in publications without any information on accuracy being given.
  • The apparent accuracy is used by measurements to consciously manipulate data and statistics. As a rule, the more bodies they present to us, the more accurate and credible statistics are.

The further processing of this data leads to problems, since many statistical methods are not based on the original data, but rather on their ranking. Due to the pseudo-accuracy of the data, a clear rank can now be assigned to each date , where previously the mean value of the ranks of several dates was assigned as a rank. This can lead to falsifications in the statistical methods used.

Examples

Robert Edwin Peary

In the diary of the polar explorer Peary it was noted that he reached the position 89 ° 57'11 "north latitude on April 6, 1909. This means that he was only about 5 km away from the North Pole and has actually reached it.

The position specification implies that Peary was able to determine his position to within an arc second . This corresponds to an accuracy of approx. 30 m. But even with the satellite-based Global Positioning System , an accuracy of only 15 m was achieved in 2000. So how could Peary achieve such accuracy with his instruments?

Answer: He couldn't exactly state his position. Today it is assumed that the accuracy of his instruments was about 15 ', i.e. that is, he could only determine his position to an accuracy of about 30 km. Coupled with other inconsistencies in his statements, there are considerable doubts as to whether Peary was really close to the North Pole.

Death statistics

Cause of death groups in Germany in 2012 from the German Cancer Atlas

According to the Federal Statistical Office , 340,217 of the total of 869,582 deaths in 2012 were due to diseases of the circulatory system. Due to the inaccuracy of the cause of death statistics, e.g. B. due to only low autopsy numbers, critics consider the first or the first two digits to be realistic at best.

Web links

  • Excessive accuracy is fatal. Steinbeis Transfer Center Innovative Systems and Services, October 14, 2009, accessed on February 28, 2010 .
  • Sham accuracy. Bissantz & Company GmbH, April 13, 2007, accessed on February 28, 2010 .

literature

  • Markus Neuhäuser, Graeme D. Ruxton: Round your numbers in rank tests: exact and asymptotic inference and ties . In: Behavioral Ecology and Sociobiology . tape 64 , no. 2 . Springer, Berlin / Heidelberg 2009, p. 297-303 , doi : 10.1007 / s00265-009-0843-1 .
  • Walter E. Krämer : That's how you lie with statistics . 12th edition. Piper, 2000, ISBN 3-492-23038-5 .

Individual evidence

  1. German Cancer Research Center: Cancer Atlas. (PDF) Retrieved November 26, 2016 .