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Table 1 Sample size needed to detect an absolute difference of 15% in the proportion of visits to a dentist (α = 5%, power = 80%)

From: An oral health intervention for people with serious mental illness (Three Shires Early Intervention Dental Trial): study protocol for a randomised controlled trial

Standard care, %

Dental intervention, %

Non-cluster N (total)

Multiplied by design effect

Adjusted for 20% dropout

5

20

176

334

418

10

25

226

430

538

15

30

268

510

638

20

35

302

574

718

25

40

330

628

785

30

45

352

670

837

35

50

366

696

870