Professor fischer observes three different age groups over a period of 10 years to chart changes in memory. what kind of research is this?

Professor Fischer uses the sequential research method. In the problem, Professor Fischer observes three different age groups over a period of 10 years periodically to take note of the changes in memory; this is a clear example of the sequential research method.  Sequential research method is also known as cross-sequential study that uses and combines the longitudinal design and cross-sectional design study.  Its purpose is to correct the problems that were inherent in the cross sectional and longitudinal designs.

Both longitudinal and cross-sectional are observational studies and researchers usually do not interfere with their subjects.  Professor Fischer’s action on observing 3 different age groups is called longitudinal study, but he also takes note of the changes, that makes him gathering the data which is most commonly a cross-sectional study. Combination of these two is called sequential study.