LGI Learning gain index. This is the gain trend as a percentage of the system gain in the base year of 1991. The mean number of students for which there is ITBS data. The output trend standard error is based on the consistency of the trend in students' outputs in the school, and the number of students for which there is data. The standard error can be used to determine the precision of the output trend estimate, and to construct a confidence interval around the estimate to determine if it is significantly different from zero.
Outputs are students' ITBS scores for the current year in the current grade.
The output trend is the average change in student outputs per year. This variable should be used to determine whether ITBS scores have been changing over time.