In addition to the following questions about TIMSS, more FAQs about international assessments are available at: http://nces.ed.gov/surveys/international/faqs.asp.
The results from NAEP and TIMSS include information on trends over time in fourth- and eighth-grade mathematics for a similar time interval: in NAEP between 1996 and 2007 and in TIMSS between 1995 and 2007. For both grades, the trends shown by NAEP and TIMSS are largely consistent with one another. Both assessments showed statistically significant increases in the mathematics performance of fourth- and eighth-grade students—overall, among boys, and among girls.
NAEP also reported increases over time for each of four racial/ethnic groups (White, Black, Hispanic, and Asian), for students at the top and bottom extremes of the distribution (at the 10th and 90th percentiles), and for students receiving free and reduced-price lunch, at both grades. The only exception was for Asian eighth-grade students, for which there was no measurable change; these results were calculated over a different time period (1992 to 2007) than the other NAEP trends. TIMSS only detected increases in mathematics performance for some of these groups (e.g., White and Black students in both grades, students in the 10th percentile in both grades) and no change for others (e.g., Hispanic fourth-grade students). This is likely to do with NAEP's larger sample sizes, which make it more sensitive to picking up small changes among nationally relevant subgroups than TIMSS, which is designed primarily to detect differences among countries.
The results from NAEP and TIMSS also provide trend information for fourth- and eighth-grade science, although covering a slightly shorter time interval in NAEP than in TIMSS. NAEP provides trends for the period 1996 to 2005 and TIMSS for the period 1995 to 2007. Compared with mathematics, the trends shown by NAEP and TIMSS in science are less consistent with one another, which may not be surprising given the differing time periods and the differences in the assessments discussed in the previous sections. For example, in fourth grade, NAEP shows that there was an increase in students' science performance both overall and among boys between 1996 and 2005, whereas TIMSS did not detect any change in performance for either of those groups from 1995 to 2007.
NAEP also reported increases in science performance for four racial/ethnic subgroups (White, Black, Hispanic, Asian/) whereas TIMSS only reported increases for Black and Asian students in the fourth grade. At the eighth-grade level, neither NAEP nor TIMSS showed any change in science performance among students overall. But in contrast to the fourth-grade results, TIMSS reported increases for Black, Hispanic, and Asian eighth-grade students, whereas NAEP only reported increases among Black students. This suggests that Hispanic and Asian eighth-grade students performed relatively better on the content unique to TIMSS than unique to NAEP.