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Table 2 Classical Test Theory & Item Response Theory Analyses of TV Computer/Video Game, and Telephone Sedentary behavior change Self-Efficacy Scale

From: Development of new physical activity and sedentary behavior change self-efficacy questionnaires using item response modeling

  

How sure are you that you have (can)...

M (SD)

CITC

Factor

Infit

Est (SE)

Television (n = 555)

     

q235

x

...limit watching TV to 1 hour at least one school day?

0.73 (0.45)

0.42

0.61

1.20

-1.27 (0.08)

q236

x

...limit watching TV to 1 hour per day for most school days?

0.64 (0.48)

0.60

0.82

0.95

-0.61 (0.08)

q231

 

...not watch TV at all for one school day?

0.63 (0.48)

0.46

0.64

1.06

-0.52 (0.08)

q237

x

...limit watching TV to 1 hour at least one non-school day, including the weekend?

0.57 (0.50)

0.55

0.75

1.11

-0.10 (0.08)

q238

 

...limit watching TV to 1 hour most non-school days, including weekend?

0.55 (0.50)

0.65

0.87

0.90

0.09 (0.21)

q232

x

...not watch TV at all for most school days?

0.48 (0.50)

0.57

0.77

1.03

0.57 (0.08)

q233

 

...not watch TV at all for one non-school day, including the weekend?

0.44 (0.50)

0.60

0.80

0.95

0.83 (0.08)

q234

x

...not watch TV at all for most non-school days, including weekend?

0.41 (0.49)

0.58

0.78

0.99

1.00 (0.08)

% Variance Explained (Factor 1/Factor 2) (62.6%/13.2%)

Cronbach's alpha/Person-separation reliability (full scale 0.83/0.78; reduced scale 0.74, 0.72)

Computer/Video Games (n = 538)

     

q243

x

...limit playing computer or video games to 1 hour at least one school day?

0.75 (0.43)

0.54

0.75

0.98

-0.70 (0.09)

q239

 

...not play computer or video games at all for one school day?

0.72 (0.45)

0.51

0.71

1.13

-0.44 (0.09)

q244

x

...limit playing computer or video games to 1 hour for most school days?

0.71 (0.46)

0.59

0.80

0.99

-0.35 (0.09)

q245

x

...limit playing computer or video games to 1 hour at least 1 non-school day, inc weekend?

0.69 (0.46)

0.59

0.80

0.98

-0.18 (0.09)

q246

 

...limit playing computer or video games to 1 hour for most non-school days, inc weekend?

0.64 (0.48)

0.58

0.78

1.02

0.19 (0.23)

q240

x

...not play computer or video games at all for most school days?

0.63 (0.48)

0.61

0.80

0.96

0.29 (0.09)

q241

 

...not play computer or video games at all for one non-school day, including the weekend?

0.61 (0.49)

0.59

0.78

1.02

0.44 (0.09)

q242

x

...not play computer or video games at all for most non-school days, including weekend?

0.57 (0.50)

0.64

0.85

0.89

0.75 (0.09)

% Variance Explained (Factor 1/Factor 2) (66.3%/10.1%)

Cronbach's alpha/Person-separation reliability (full scale 0.85/0.79; reduced scale 0.78, 0.73)

Telephone (n = 520)

     

q251

x

...limit talking on the telephone to 1 hour at least one school day?

0.76 (0.43)

0.55

0.77

1.07

-0.91 (0.09)

q252

 

...limit talking on the telephone to 1 hour for most school days?

0.68 (0.47)

0.60

0.81

1.02

-0.27 (0.09)

q254

x

...limit talking on the telephone to 1 hour for most non-school days, including weekend?

0.68 (0.47)

0.62

0.83

0.97

-0.23 (0.24)

q253

 

...limit talking on the telephone to 1 hour at least one non-school day, including weekend

0.67 (0.47)

0.61

0.82

0.98

-0.15 (0.09)

q247

x

...not talk on the telephone at all for one school day?

0.65 (0.48)

0.59

0.79

1.13

0.02 (0.09)

q248

x

...not talk on the telephone at all for most school days?

0.63 (0.48)

0.46

0.63

1.20

0.21 (0.09)

q249

 

...not talk on the telephone at all for one non-school day, including the weekend?

0.58 (0.49)

0.58

0.77

1.04

0.58 (0.09)

q250

x

...not talk on the telephone at all for most non-school days, including weekend?

0.56 (0.50)

0.62

0.82

1.00

0.75 (0.09)

  1. % Variance Explained (Factor 1/Factor 2) (65.9%/10.5%)
  2. Cronbach's alpha/Person-separation reliability (full scale 0.84/0.75; reduced scale 0.75, 0.71)
  3. Corrected item total correlation [CITC]; item response modeling item difficulty estimate [Est (SE)
  4. Infit statistic (acceptable range between 0.75 and 1.33)
  5. Self efficacy item scale: not sure (0), sure (1); "x" represents item retained in reduced scale