The research question — whether viewpoints on decriminalization of marijuana for medical purposes change with age — is interesting, but the study design described has a major flaw : it uses different age groups of different people , rather than following the same individuals over time.

The Flaw: Cross‑Sectional vs. Longitudinal Design

This study is cross‑sectional , meaning it compares four separate groups (ages 20, 30, 40, and 50) at one point in time. That design cannot actually determine whether attitudes change with age , because:

  • Differences among the groups might reflect generational or cohort effects — people born in different decades have different cultural, political, and social backgrounds.
  • It doesn’t show how any one person’s viewpoint evolves as they grow older.

To truly assess how age changes opinions , researchers would need a longitudinal study , tracking the same participants over several decades to see whether and how their views shift.

Example Illustration

Let’s say:

  • 20‑year‑olds mainly support legalization,
  • 50‑year‑olds mostly oppose it.

In a cross‑sectional snapshot, that difference could mean:

  • Older people become more conservative as they age (age effect) , or
  • People born 50 years ago have always been more conservative (cohort effect).

Without tracking the same individuals, you cannot tell which is true. ✅ In short:

The major flaw is that this cross‑sectional design compares different age groups rather than observing the same participants over time, so it confounds age effects with cohort (generation) differences.

Information gathered from public forums or data available on the internet and portrayed here.