Dr. edward is testing the same individuals repeatedly over time as part of a research study, while dr. janice is comparing the performance of different people of various ages at the same time. dr. edward is using a research method;

Longitudinal research

Explanation:

Longitudinal research is also called an observational study method. In this research, the data is gathered on the same population over some time. Longitudinal study as the name indicated run for a long-time period or a decade. In this study, the same individual is observed for a long period.  

For instance, a study was conducted on aging in which around five thousand people were part of the study between the age of 45 to 85 for 20 years,  

Thus Dr. Edward used a longitudinal study to conduct his research.

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