Development of the 8-Item Phlegm Pattern Questionnaire (PPQ-8) Using Rasch Analysis

Figure 1

Probability curves of the 7-point (a) and 6-point (b) responses. C1 (category 1), disagree very strongly; C2 (category 2), disagree strongly; C3 (category 3), disagree; C4 (category 4), neither disagree nor agree; C5 (category 5), agree; C6 (category 6), agree strongly; and C7 (category 7), agree very strongly. The arrow indicates the peak of the C4 curve in 1B.

(a)

(b)