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Published on: May 2, 2013
Modeling and correction of digit preference in tuberculin surveys
1Department of Medical Statistics, Leiden University Medical Centre, Leiden, The Netherlands. p.eilers@lumc.nl
Setting:
Human observers generally have a strong tendency to round analog measurements or estimates to 'nice' ending digits, such as 0, 5, or even numbers. This is known as digit preference; it is a well-known phenomenon in frequency distributions of indurations collected in tuberculin surveys. Digit preference can distort estimates of prevalence and other statistical parameters.
Methods:
We have developed a statistical model that combines smoothing by penalized likelihood and the transfer of counts from non-preferred to preferred digits, to obtain estimates of: 1) the smooth underlying distribution and 2) the amount of digit preference.
Results:
To illustrate the validity of the model, it was applied to data from several countries.
Conclusion:
With the proposed model, digit preference can be quantified and frequency distributions of indurations can be corrected for it.
