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Table 4 Results of tests of item convergent validity, item discriminant validity, reliability, and floor and ceiling effects for the EAPIQ (total sample)

From: The reliability, validity, and preliminary responsiveness of the Eye Allergy Patient Impact Questionnaire (EAPIQ)

  

Item-level

  

Scale-level Reliability

 

Scale-level

 

EAPIQ scale

No. of Items

Convergent validitya

 

Discriminant validityb

Internal consistency

Test-retest

Floor effects

Ceiling effects

  

Range of correlations

Success rate (%)

Success rate (%)

Cronbach's alpha

ICC

%

%

Symptomsc

5

0.53–0.77

100

90

0.84

0.75

11.3

0.7

Daily Life Impactc

6

0.57–0.78

100

83.3

0.88

0.84

15.5

0.0

Psychosocial Impactc

6

0.58–0.75

100

91.7

0.88

0.85

28.2

0.0

Treatment Satisfactiond

3

0.84–0.86

100

100

0.93

0.72

1.7

0.0

  1. a Percentage of item-scale correlations ≥ 0.40.
  2. b Percentage of item-scale correlations (adjusted for overlap) higher with the item's own scale than with any other EAPIQ scale
  3. c Sample size of 142 patients who completed more than half of the items in the Daily Life Impact, Psychosocial Impact and Symptoms scales.
  4. d Sample size of 119 patients who completed more than half of the items in the Daily Life Impact, Psychosocial Impact and Symptoms and Satisfaction scales.
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Health and Quality of Life Outcomes

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