If a researcher was interested in learning how moral development changes between the ages of 3 and 15, the researcher might study a group of children until they are 15, testing them periodically. This research strategy is known as research.

The answer is longitudinal research.

Explanation:

Longitudinal research is done over a period of time and usually involves observing a small group of subjects. These are especially common in social sciences such as sociology and psychology, although other areas like medicine also use longitudinal studies to examine the effects of diseases or treatments.

The greatest advantage of longitudinal studies is that they are often unexpensive and highly reliable, as they involve constant and rigurous observation. However, they are naturally time consuming and might not accurately reflect larger populations.

explanation:

- "ethical issues. deception – the participants actually believed they were shocking a real person and were unaware the learner was a confederate of milgram's. however, milgram argued that “illusion is used when necessary in order to set the stage for the revelation of certain difficult-to-get-at-truths.” "

- "milgram's work was conducted in the early 1960s before the current.the studies ignited a debate about the ethical treatment of participants. what appear to be dangerous, if not deadly, electric shocks and the by today's ethical standards, many questions about the research have gone unanswered."