Polska Grupa Badawcza is an opinion poll institute in Poland. It claims to use the most rigorous testing and frequency criticizes all other Polish opinion poll institutes for lacking methodologies.
Accuracy
Since 2004 Centrum im. Adama Smitha publishes accuracy analyses of predicted election results, using sum of errors of predictions of results of the individual parties as a benchmark (grouping all parties that scored below certain threshold as "other parties").
PGB's predictions of results of the last few elections in Poland were usually more accurate than other institutes'. Most notably, it was the only one institute that correctly predicted election of Lech Kaczyński in the 2005 presidential elections, all other polls incorrectly predicting victory of Donald Tusk.
In elections to the European Parliament in 2004, PGB had total error of 24.9%, compared to 30.0%-36.6% by six other opinion poll institutes.
In 2005 parliamentary elections, PGB had slightly smaller error of 21% compared to other institutes' 21%-23%.
In the first round of presidential elections it had relatively bad result, with error of 17% compared to others' 11%-17%, however it was closest to correctly predicting the run-off, with 8% error, compared to others' 12%-16%, and the only one to correctly determine the winner.