[Fis] definitions of information by Theil (1972) derived from Shnnon (1948); back to the basics?
Loet Leydesdorff
loet at leydesdorff.net
Mon Jan 23 16:29:38 CET 2023
Theil (1972) pp. 1 and 2:
1.1. Information
Consider an event E with probability p; the nature of the event is
irrelevant. At some point in time we receive a reliable message stating
that E in fact occurred. The question is: How should one measure the
amount of information conveyed by this message?
Information
Since the question is vague, we shall try to answer it in an intuitive
manner. Suppose that p is close to 1 (e.g., p = .95). Then, one may
argue, the message conveys very little information, because it was
virtually certain that E would take place. But suppose that p = .01, so
that it is almost certain E will not occur. If E nevertheless does
occur, the message stating this will be unexpected and hence contains a
great deal of information.
These intuitive ideas suggest that, if we want to measure the
information derived from a message in terms of the probability p that
prevailed before or to the arrival of the message, we should select a
decreasing function. The function proposed by SHANNON (1948) is when the
probability prior to the message is zero) to 0 (zero information when
the probability is one).
The unit of information is determined by the base of the logarithm.
Frequently 2 is used as a base, which implies that any message
concerning a 50-50 event has unit information: h() = log2 2 = 1, and
information is then said to be measured in binary digits or, for short,
bits. When natural logarithms are used, the information unit is a nit.
best, loet
_______________
Loet Leydesdorff
"The Evolutionary Dynamics of Discusive Knowledge"
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Professor emeritus, University of Amsterdam
Amsterdam School of Communication Research (ASCoR)
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