What is most likely the biggest problem with longitudinal ...

[Mr3Hunna]

What is most likely the biggest problem with longitudinal research?
 
  changing ages of participants
  not being able to keep participants over time
  changing historical context
  participants becoming aware of the goals of the study and changing their
  behaviors or answers

Question 2

A cross-sequential design:
 
  examines a single group of people who are the same age at one point in time.
  examines two or more groups of people who are of different ages at one point
  in time.
  follows a single group of people over an extended period of time.
  follows two or more groups of people who are of different ages over a period of
  time.

[joshraies]

Answer to Question 1

changing historical context

Answer to Question 2

follows two or more groups of people who are of different ages over a period of
time.