The OECD Programme for International Student Assessment (PISA) survey takes place every three years, examining the ability of 15 year-olds from around the world to extrapolate from what they have learned and apply that knowledge in unfamiliar settings, both inside and outside school. The PISA survey covers three main subjects: mathematics, reading and science. In each round, one of these subjects is the major domain and the other two are minor domains. The latest set of results from the 2012 data collection (PISA 2012) focuses on mathematics and compares the competencies of students in 65 countries and economies. Around 510 000 students between the ages of 15 years 3 months and 16 years 2 months participated in PISA 2012, representing about 28 million 15-year-olds globally. Interpretation of the results: The country results are estimates because they are obtained from samples of students, rather than from a census of all students, and they are obtained using a limited set of assessment tasks, not a population of all possible assessment tasks. The standard errors (S.E.) used for the interpretation of these differences are available from PISA 2012 results.