A secular trend is a

A secular trend is a
 
  a. decrease in religiosity
  b. trend in the general population
  c. trend that increases and decreases in a regular pattern, such as the seasons
  d. time-lag effect

Question 2

Longitudinal studies have the theoretical problem that
 
  a. Age is confounded with time of testing
  b. It's difficult to recruit people for such a study
  c. They are expensive
  d. They take a long time to complete

Question 3

A __________ study tests the same group of individuals over a long period of time.
 
  a. cross sectional
  b. longitudinal
  c. cross sequential
  d. cohort