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Calculation of test quality criteria for screenings


Screening procedures aim at identifying persons who have a certain (binary) characteristic. They are often used to identify people at risk who later develop mental disorders, diseases or school problems. For the evaluation of the screenings there are a number of characteristic values, of which sensitivity and specificity are the best known. They show how many people were correctly identified by the test as risk and how many as non-risk persons.

Besides these basic data, however, there are a number of other important data, such as the positive and negative predictive values or the Matthews Correlation Coefficient (MCC, relative increase in the hit rate compared to the random hit rate; further information and a detailed description of the various parameters can be found in Marx & Lenhard, 2010).


Online calculator to determine specificity, specificity, predictive value and MCC

You can use the table to determine various characteristic values for screening procedures. Please enter the absolute case numbers in the table cells.

Area proportions see graphic
please fill in absolute numbers
Predictor
(e. g. from a screening)
positive result negative result
Criteria not affected b

(false positive)
d

(correct negative)
affected a

(correct positive)
c

(false negative)


Quality indicators of the screening:
Sensitivity
Specificity
positive predictive value
negative predictive value
Hit ratio
Random hit ratio
Matthews correlation coefficient (MCC)


Explanation:


Online tool as Excel table and Java source code

The online tool is available as an Excel sheet and as Source-Code in Java under the General Public License (GPL):



Literature

Marx, P. & Lenhard, W. (2010). Diagnostische Merkmale von Screeningverfahren. In M. Hasselhorn & W. Schneider (Hrsg.), Frühprognose schulischer Kompetenzen. Göttingen: Hogrefe.

Citeable: Lenhard, W. & Lenhard, A. (2014). Calculation of test quality criteria for screenings. available: http://www.psychometrica.de/testkennwerte.html. Dettelbach: Psychometrica.