The article deals with the public opinion research before 1989 in then Czechoslovakia. The most important public opinion re- search institution of its time is the subject of discussed analysis, i.e. The Institute for Public Opinion Research, which operated in the framework of several institutional arrangements during the period 1946 to 1990 (in the 1970s also with the name changed to the Public Opinion Research Cabinet).
Turnout probability measurement is one of the fundamen- tal methodological questions of pre-election polls. Accurate pre-election polls are important not only for polling agencies and politicians but also for social scientists. Among the op- portunities they indeed provide is verifying the accuracy of questionnaire surveys – one of the fundamental social scien- tific methods.