Table 2 Psychometric properties of the CSI scale

Item properties

# of items in the scale

5

4

4

8

13

% of questionnaires with at least ½ the items completed

99.6%

97.6%

98.1%

97.9%

98.1%

# of questionnaires with ½ + 1 items completed

530

510

513

523

524

# of items with “missing data” > 20%

0

0

0

0

0

# of items with “does not apply” response > 20%

0

0

0

0

0

# of item with ceiling effect > 50%

0

0

4

4

4

# of item with floor effect > 50%

0

0

0

0

0

Scaling properties

Mean score (±SD)

49.3 (17.9)

69.3 (23.1)

86.9 (15.5)

78.1 (15.8)

-

Skewness value/SE

0.25/0.78

-0.59/0.78

-1.01/0.78

-0.38/0.78

-

Median

46.2

66.1

91.5

78.7

-

Ceiling effect (%)

0.9%

15.7%

47.7%

13.9%

-

Floor effect (%)

0%

1.2%

0%

0%

-

# of item correlation with own scale > 0.40

5

4

4

-

-

# of item correlation with own scale greater than with other scale

5

4

4

-

-

Cronbach’s α coefficient

0.80

0.87

0.81

0.83

-

Sum of square of the factors before rotation

31.6%

18.6%

13.5%

-

63.7%

% of variance explained by the factor

22.4%

21.7%

19.6%

-

63.7%

Test of unidimensionality

1st eigenvalue

2.81

3.01

2.64

3.52

-

2nd eigenvalue

0.78

0.43

0.76

1.83

-

Dillon-Goldstein’s Rho

0.87

0.92

0.88

0.88

-