Table 16 Sept 2026From “What is external validity? A result needs a transfer boundary”

Which four dimensions change the transfer question?

Table 1Which four dimensions change the transfer question?

Dimension	Object that can change	Diagnostic question	Typical hidden substitution
X-validity	Population or unit	Who was in the source, and who is in the target?	Trial users become enterprise accounts
T-validity	Treatment or implementation	Is the target intervention the same treatment in the relevant sense?	An email sequence becomes a sales-led program
Y-validity	Outcome or measurement	Is the target outcome the same construct, event, and horizon?	First report exported becomes 90-day renewal
C-validity	Context or setting	Could geography, institution, channel, language, regulation, or time change the mechanism?	One market's operating conditions become another's

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Source: Table from this essay. Sources and interpretation are given in the article.

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What is external validity? A result needs a transfer boundary

External validity asks whether a result transfers across a named population, treatment, outcome, and context. Name the target before generalizing.

6 Sept 2026

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Isoglu, S. (2026). Which four dimensions change the transfer question? [Table]. isoglu.com. https://isoglu.com/insights/exhibits/isoglu-2026-what-is-external-validity-fig01/

BibTeX

@misc{isoglu-2026-what-is-external-validity-fig01,
  author = {Isoglu, Sinan},
  title = {{Which four dimensions change the transfer question?}},
  year = {2026},
  howpublished = {Table 1, isoglu.com},
  url = {https://isoglu.com/insights/exhibits/isoglu-2026-what-is-external-validity-fig01/},
  note = {From the essay {What is external validity? A result needs a transfer boundary}}
}

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