How are countries/economies ranked in PISA?
PISA ranks participants according to their performance in reading, mathematics and science, as well as problem solving in PISA 2003. PISA does not give a collective score for all subjects combined; rather it gives a score for each subject area and countries are ranked by their mean score in each area. However, it is not possible to assign a single exact rank in each subject to each country. This is because PISA tests only a sample of students from each country and this result is then adjusted to reflect the whole population of 15-year-old students in that country. The scores thus reflect a small measure of statistical uncertainty and it is therefore only possible to report the range of positions (upper rank and lower rank) within which a country can be placed. For example, in PISA 2003 Finland and Korea were widely reported as ranking 1st and 2nd in PISA, when in fact we can only say that, among OECD countries, Finland’s rank was between 1st and 3rd and Korea’s was between 1st and 4th.
