Results
The purpose of the study was to confirm the structure of the instrument by way of confirmatory factor analysis (CFA). Also, we intended to test if the structure is invariant across the two populations (Normal and learning difficulty). Several indexes of goodness of fit were used to evaluate the model. We specified seven factors representing the six domains and the seven the factor for achievement in math and Arabic. The model assumed a correlated factors model. Also, parcels were used instead of items. Some parcels were sum of two items and some were sum of three items. Therefore the domains (perception, attention, memory and writing) were measured by four parcels and the domains (Reading and math) were measured by five parcels. Achievement was measured by two observed scores: Arabic and math.