Research data that may be categorized, ranked, or numbered is:

What is a disadvantage of longitudinal research?

a. People are likely to drop out, so the sample size can be greatly reduced. b. It is relatively cheap, so other researchers don't take it seriously. c. Over time, more people want to join the study and there often end up being too many participants. d. With so much data, it is difficult to see trends over time within participants.

_________ increases by only 10 percent during middle childhood and adolescence

A) White matter B) The weight of the brain C) Gray matter D) The number of synapses