Answer:
She is using a cross-sectional research design.
Explanation:
In cross-sectional research, researchers gather data from different population groups in one point in time. The variable defining the different population groups can be gender or race, but it is mostly age, like in professor Grant's study, who is collecting data of four different groups according to their age. Cross-sectional research can be used to compare the results of the population groups and it is commonly used in developmental psychology.
