. 2009 Jan 27;36(4):811–829. doi: 10.1093/schbul/sbn181

Table 2.

Threats to Internal and External Validity of Studies Meeting Inclusion Criteria

		Internal	Internal		Internal	External
Cohort	No Item Screening or Appraisal	Biased Analysis Method	Insufficient Models Compared	Conditional Independence Not Tested	Commingled Sample	Constraint on Population
Young¹³	✓	✓	✓	✓		✓
Goldstein et al³¹	✓	✓	✓	✓		✓
Jørgensen and Jensen³²	✓	✓	✓	✓		✓
Parker et al³³		✓	✓	✓		✓
Castle et al³⁴	✓	✓	✓	✓		✓
Goldstein et al³⁵		✓	✓	✓	✓	✓
Nestadt et al³⁶
Schizoid items	✓	✓	✓	✓		✓
Paranoia items	✓	✓	✓	✓		✓
Schizotypal items	✓	✓	✓✓	✓		✓
All items	✓	✓	✓✓	✓		✓
Tyrka et al³⁷					✓	✓
Bell³⁸ study 1	?			?
Bell³⁸ study 2	?			?
Bell³⁸ study 3	?			?	✓
Kendler et al³⁹
Schizophrenia subset	✓	✓	✓✓✓	✓		✓
Nonaffective subset	✓	✓	✓✓✓	✓		✓
Kendler et al⁴⁰	✓	✓	✓	✓	✓	✓
Battaglia et al⁴¹	✓	✓		✓
Fossati et al⁴²	✓	✓		✓		✓
Peralta et al⁴³
Index episode	✓	✓		✓		✓
Lifetime	✓	✓		✓		✓
Interepisode	✓	✓		✓		✓
Peralta and Cuesta⁴⁴ and Cuesta et al⁴⁵
Index episode, LCA	✓	✓		✓		✓
Lifetime, LCA	✓	✓		✓		✓
Factor scores, CCK	✓			✓		✓
Blanchard et al⁴⁶				✓	✓	✓
Fossati et al⁴⁷ study 1
Interview data		✓				✓
Self-report data		✓				✓
Fossati et al⁴⁷ study 2		✓	✓			✓
Fossati et al⁴⁷ study 3		✓	✓
Haro et al⁴⁸		✓	✓✓✓		✓	✓
Murray et al⁴⁹	✓	✓	✓✓✓	✓	✓	✓
Boks et al⁵⁰	✓	✓				✓
Schmitz et al⁵¹ primary		✓		✓		✓
Schmitz et al⁵¹ replication		✓		✓		✓
Shevlin et al⁵²^,⁵³ NCS
Hybrid IRT-LCA	✓		✓
LCA	✓	✓		✓
Shevlin et al⁵² NEMESIS	✓		✓

Note: LCA, latent class analysis; CCK, coherent cut kinetics; NCS, National Comorbidity Survey; NEMESIS, Netherlands Mental Health Survey and Incidence Study; IRT-LCA, item response theory-latent class analysis