Answer:
Repeated measures design
Explanation:
Repeated measures design otherwise known as Within-subject design, is a form of research design in which multiple measurements of the same variable taken on the same or matched group of subjects, either under different conditions or over two or more time periods.
In other words, it is a form of research design in which the same group of participants take part in each condition of the independent variable.
Hence, in this case, since John is letting the same participants to take part in the different conditions of independent variable, which is sorting techniques, so as to determine, which of the sorting techniques leads to better memory performance in pre-teens, this is considered as REPEATED MEASURE DESIGN.
