[4] It is therefore equal to the information contained in one decimal digit (or dit), assuming a priori equiprobability of each possible value.
[5][6] The ban and the deciban were invented by Alan Turing with Irving John "Jack" Good in 1940, to measure the amount of information that could be deduced by the codebreakers at Bletchley Park using the Banburismus procedure, towards determining each day's unknown setting of the German naval Enigma cipher machine.
The name was inspired by the enormous sheets of card, printed in the town of Banbury about 30 miles away, that were used in the process.
[7] Good argued that the sequential summation of decibans to build up a measure of the weight of evidence in favour of a hypothesis, is essentially Bayesian inference.
[7] Donald A. Gillies, however, argued the ban is, in effect, the same as Karl Popper's measure of the severity of a test.