Steve Tippins Ph.D.Helping doctoral students get their dissertation accepted, succeed in their careers, & change the world | Academic Career Advisor | Dissertation Chair & Founder, Beyond PhD Coaching | 35 + years of experience.

Preventing Sampling Problems for External Validity

13 Feb 2026 · 0 min

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Excluding protected groups like pregnant women, prisoners, and minors from research makes it harder to replicate studies and limits what findings apply to the real world. Ethical rules keep these groups out, but that exclusion itself becomes a problem for external validity.

For external validity. We want to avoid sampling problems. We want to make sure we have a group of people that we are allowed to sample. There are protected groups like pregnant women, prisoners, minors, things like that. Getting them involved in a study is much more difficult, so replication also becomes more difficult. Drop the word help in the comments and I'll send you a link to my free dissertation help community.