Jessica Hillyer and Robin L. Joynes conduct research on animals with injuries to their spinal cords, with the goal of helping learn how organisms, including humans, may be able to improve their physical movements (locomotion) after injury. One difficulty that they noted in their research with rats was that the existing measure of locomotion (the BBB Locomotor Rating Scale, (BBB), Basso, Beattie, & Bresnahan, 1995) was not sophisticated enough to provide a clear measure of locomotion skills. They therefore decided to create their own, new, measure, which they called the Hillyer-Joynes Kinematics Scale of Locomotion (HiJK). Their measure was designed to assess the locomotion abilities of rats walking on treadmills.
The researchers began by videotaping 137 rats with various degrees of spinal cord injuries as they walked on treadmills. Then three different coders viewed each of the videotapes on a subset of twenty of the rats. For each of these 20 rats, the coders rated the walking skills of the rats on eight different dimensions: Extension of the Hip, Knee, and Ankle joints, Fluidity of the joint movement, Alternation of the legs during movement, Placement of the feet, Weight support of the movement and Consistency of walking.
Once the raters had completed their ratings, the researchers tested for interrater reliability, to see if the three raters agreed on their coding of each of the five categories that they had rated. Overall, they found high interrater reliability, generally with r’s over .9. For instance, for the ratings of foot placement, the correlations among the three coders were as follows:
Rater 1 Rater 2
Rater 2 .95
Rater 3 .95 .99
The researchers then had one of the three raters rate all 137 of the rats on the 8 subscales. On the basis of this rater’s judgments, they computed the overall reliability of the new measure, using each of the eight rated dimensions as an item in the scale. The Cronbach’s alpha for the composite scale, based on 8 items and 137 rats was a 5 .86, denoting acceptable reliability.
Having determined that their new measure was reliable, the researchers next turned to study the validity of the scale. The researchers found that the new measure correlated signifi cantly with scores on the existing measure of locomotion, the BBB Locomotor Rating Scale, suggesting that it was measuring the locomotion of the rats in a similar way that it did.
Finally, the researchers tested for predictive validity, by correlating both the BBB and the HiJK with a physiological assessment of the magnitude of each of the rat’s spinal cord injuries. The researchers found that the HiJK was better able to predict the nature of the rats’ injuries than was the BBB, suggesting that the new measure may be a better measure than the old one. ( Reliability and Validity )
