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Table 7 Convergent validity: correlations between more and less conceptually related measures at Days 1, 4 and 8

From: Patient-reported outcomes to assess the efficacy of extended-release guaifenesin for the treatment of acute respiratory tract infection symptoms

  Daily Cough and Phlegm Diary – 8 items
  Symptom subscale – Day 1 Symptom subscale – Day 4 Symptom subscale – Day 8
Spontaneous symptom assessment: congestion 0.15* 0.50‡ 0.64‡
Spontaneous symptom assessment: mucus 0.19† 0.42‡ 0.59‡
Spontaneous symptom assessment: cough 0.20† 0.52‡ 0.57‡
Patient’s End-of-Treatment Assessment 0.07 −0.17* −0.32‡
WURSS-21 Total 0.50‡ 0.68‡ 0.70‡
WURSS-21 Symptom 0.44‡ 0.65‡ 0.69‡
WURSS-21 Function 0.45‡ 0.61‡ 0.61‡
Investigator’s End-of-Study Assessment −0.04 −0.20† −0.37‡
  1. WURSS-21: the Wisconsin Upper Respiratory Symptom Survey. Spearman rank-order correlations: *p < 0.01, †p < 0.001, ‡p < 0.0001.