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Table 2 Physical function instruments, metric scores, and sample size requirements

From: Improved responsiveness and reduced sample size requirements of PROMIS physical function scales with item response theory

  Standardized response mean Cohen's effect size Guyatt's effect size Minimum detectable difference Sample size requirement n (95% CL1)
Legacy PF-10 0.10 0.06 0.49 2.43 427 (345, 514)
Legacy HAQ 0.14 0.06 0.52 1.40 143 (113, 176)
Item-Improved PF-10 0.09 0.05 0.59 2.16 336 (245, 436)
Item-Improved HAQ 0.13 0.05 0.73 1.14 95 (76, 117)
PROMIS PF 10 0.13 0.05 0.52 1.47 157 (127, 189)
PROMIS PF 20 0.13 0.05 0.63 1.24 113 (90, 141)
  1. 1 Confidence Limits
  2. HAQ, health assessment questionnaire; Item-Improved, Changes to items intended to improve their performance by altering parameters such as time frame and response options while retaining the same item stem; PF, physical function; PROMIS, Patient-Reported Outcomes Measurement Information System.