| | Fidelity sampling method (, % of total studies) | Study references |
| | Purposive sampling (, 5%) | Studies 44 and 46 | | Random sampling (, 14%) | Studies 2, 3, 9, 14, 20, 28, 33, and 34 | | Included the whole sample (, 24%) | Studies 23, 24, 35, 37, 40, 42, 45, and 49–54 | | Specified they were assessing fidelity amongst intervention providers in the sessions delivered (, 5%) | Studies 42 and 47 | | Specified assessing fidelity in participant groups receiving the intervention (, 5%) | Studies 43 and 44 |
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