In formulating researchable questions that explore the discrepancy in the use of digital textbooks in primary schools, Sizwe should focus on factors that could influence the effectiveness of digital textbooks. Among the options provided, the one he should NOT consider is:
The brand of digital devices used to read the textbooks.
While the brand of devices might impact user experience to some extent, it is less likely to be a core factor influencing educational outcomes compared to aspects such as socio-economic status, subject matter, teaching methodologies, and the age of students. These latter factors have a more direct influence on how effective digital textbooks are in enhancing learning.