*p < .05. Difference in percentages is significant at the .05 level of statistical significance.

¹ The advanced mathematics coverage index is the percentage of the corresponding age cohort covered by students in their final year of secondary school who have taken or are taking advanced mathematics courses. The corresponding age cohort is determined for education systems individually. In the United States, the corresponding age cohort is considered 18-year-olds. For additional details, see the Technical Notes available at http://nces.ed.gov/timss/timss15technotes.asp.

² Years of formal schooling are counted from the first year of primary or basic education (the first year of ISCED [International Standard Classification of Education] level 1). Because of ongoing reforms in some education systems to increase the number of years of schooling, the number of years of formal schooling is not always the same as the grade assessed.

³ The difference in percentages is calculated by subtracting the females' estimate from the males' estimate using unrounded numbers.

⁴ Intensive courses are advanced mathematics courses that involve 6 or more hours per week. Results for students in these courses are reported separately from the results for other students from the Russian Federation taking courses that involve 4.5 hours per week.

⁵ Did not satisfy guidelines for sample participation rates.

⁶ Met guidelines for sample participation rates only after replacement schools were included.

NOTE: Standard error is abbreviated as s.e.

SOURCE: International Association for the Evaluation of Educational Achievement (IEA), Trends in International Mathematics and Science Study (TIMSS) Advanced, 2015.