Notes for students. International large scale assessments (ILSAs) have several characteristics that should be accounted for to generate correct results. The characteristics that are important to account for include: 1) the use of plausible values; 2) the use of weights; and 3) the cluster sampling used. Some of the datasets that this applies to include TIMSS, PISA, PIRLS, and even NAEP (not international). Certain packages can also be used (e.