Design 1:  cross-sectional
           (different age groups all measured that the same time)

                d.v. = % with NO religious affiliation
 

20-30  (1995)                     4.8%
 

40-50  (1995)                     3.1%
 

60-70  (1995)                     1.9%
 

80+    (1995)                     1.2%
 
 
 

Design 2:  Longitudinal
           (SAME people tested at different times)
 

                 d.v. = NO religious affiliation
 

20-30  (1935)              4.8%
 

40-50 (1955)               11.9%
 

60-70 (1975)               11.9%
 

80-90  (1995)               12.2%