This technical note gives details of the reliability and validity of the assessments used in the
second school survey carried out by Young Lives in Ethiopia for the purpose of the
construction of test scores on a common scale within each language for maths and reading
comprehension. This document give details of the three-parameter model used to build the
achievement scores in both content areas. We tested graphically for item fit and item bias (by
gender and wave). Our results indicate that most of the items used have a good item fit as
well as they did not show the presence of bias by wave or gender. Finally, we did an external
validity analysis correlating the IRT scores (maths and reading comprehension) with
individual and family characteristics, and the results showed that correlations were
statistically significant with the expected signs.