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. Author manuscript; available in PMC: 2015 Feb 1.
Published in final edited form as: Qual Life Res. 2013 Jun 6;23(1):349–361. doi: 10.1007/s11136-013-0439-0

Table 4.

Physical functioning DIF analysis

Short form Item stem Age DIF (5–7 vs. 8–17)
Age DIF (8–12 vs. 13–17)
X2 (df) p X2 (df) p
Upper extremity
SF My child could put on his/her shoes without help. 3.9 (5) 0.56 0.1 (5) 1.00
SF My child could button his/her shirt or pants. 3.6 (5) 0.61 0.3 (5) 1.00
My child could put on his/her clothes without help. 2.6 (5) 0.76 2.3 (5) 0.80
My child could pull on and fasten his/her seatbelt. 3.6 (4) 0.47 2.0 (4) 0.73
My child could put on his/her socks without help. 6.5 (5) 0.26 1.2 (5) 0.94
My child could use a mouse or touch pad for the computer. 1.5 (3) 0.68 2.7 (3) 0.44
My child could wash his/her face with a cloth. 3.0 (3) 0.40 1.8 (3) 0.61
SF My child could use a key to unlock a door. 12.7 (5) 0.03 2.6 (5) 0.77
SF My child could open the rings in school binders. 8.6 (5) 0.13 2.9 (5) 0.72
My child could tie shoelaces without help. 6.4 (5) 0.27 2.6 (5) 0.77
My child needed help with a bath. 8.6 (5) 0.13 3.8 (5) 0.58
SF My child could pull open heavy doors. 9.0 (5) 0.11 1.7 (5) 0.88
My child could move his/her hands or fingers. 3.4 (3) 0.33 4.0 (3) 0.26
My child used a pencil with a special grip to write. 3.1 (5) 0.68 3.5 (5) 0.62
My child could hold a full cup. 4.0 (3) 0.37 5.0 (3) 0.17
My child could open his/her clothing drawers. ** ** ** **
SF My child could pour a drink from a full pitcher. ** ** ** **
My child could dry his/her back with a towel. ** ** ** **
My child could turn door handles without help. ** ** ** **
SF My child could open a jar by himself/herself. ** ** ** **
My child could brush his/her teeth without help. ** ** ** **
My child could write with a pen or pencil. ** ** ** **
SF My child could pull a shirt on over his/her head without help. *** *** *** ***
My child could zip up his/her clothes. *** *** *** ***
My child could put toothpaste on his/her toothbrush without help. *** *** *** ***
My child could cut paper with scissors. *** *** *** ***
My child could lift a cup to drink. *** *** *** ***
My child could hold an empty cup. *** *** *** ***
Upper extremity DIF items
My child could dial a phone. 17.0 (4) 0.00 4.4 (4) 0.35
Mobility
SF My child could stand up without help. 3.2 (3) 0.36 1.2 (3) 0.75
SF My child could walk up stairs without holding on to anything. 3.4 (5) 0.64 5.4 (5) 0.37
SF My child could stand up on his/her tiptoes. 1.4 (5) 0.92 3.7 (5) 0.60
My child could get up from a regular toilet. 9.1 (4) 0.06 36.7 (4) 0.00
My child could get down on his/her knees without holding on to something. 4.2 (5) 0.53 7.6 (5) 0.18
SF My child could move his/her legs. 1.1 (4) 0.90 4.8 (4) 0.31
My child could ride a bike. 0.9 (5) 0.97 3.7 (5) 0.59
My child could bend over to pick something up. ** ** ** **
My child could get in and out of a car. ** ** ** **
My child could walk more than one block. ** ** ** **
My child used a wheelchair to get around. ** ** ** **
My child could get out of bed by himself/herself. ** ** ** **
SF My child could keep up when he/she played with other kids. ** ** ** **
My child could carry his/her books in a backpack. ** ** ** **
My child could get into bed by himself/herself. *** *** *** ***
My child could walk across the room. *** *** *** ***
SF My child could get up from the floor. *** *** *** ***
SF My child has been physically able to do the activities he/she enjoys most. *** *** *** ***
My child used a walker, cane or crutches to get around. *** *** *** ***
My child could turn his/her head all the way to the side. **** **** **** ****
Mobility DIF items
SF My child could do sports and exercise that other kids his/her age could do. * 17.3 (5) 0.00 2.0 (5) 0.85
My child could go up one step. * 12.7 (3) 0.01 1.4 (3) 0.71
My child could run a mile. 52.9 (5) 0.00 1.4 (5) 0.92

Item exhibited DIF between higher age groups only.

*

Items that exhibited statistical DIF that were retained with caution.

**

Form 4 items are not included due to insufficient sample size.

***

Items are not included due to slope estimates larger than 10.

****

Item is not included due to only one observed response category.