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Table 2 Test re-test reliability of pre-treatment Sleep Quality Scale scores

From: Psychometric properties of a single-item scale to assess sleep quality among individuals with fibromyalgia

Study Between-Subjects Error Variance Within-Subject Error Variance ICC of a Single Daily Score ICC for the Average of Seven Daily Scores
1056 2.40 1.68 0.59 0.91
1077 2.23 1.69 0.57 0.90
  1. ICC = Intraclass Correlation Coefficient = (Between-Subjects Error Variance)/(Between-Subjects Error Variance + Within-Subject Error Variance)
  2. ICC for the Average of Seven Daily Scores = 7(ICC for single score)/[1 + 6(ICC for a single score)]