COMBI >> Scales >> Overt Behaviour Scale >> Properties


Glenn Kelly , PhD, Diverge Consulting Inc. at

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Kelly, G. (2010). The Overt Behaviour Scale. The Center for Outcome Measurement in Brain Injury.
combi/obs ( accessed ).





OBS Properties

To date, the main psychometric evaluation of the OBS was that published in Kelly et al. (2006). Two adult community-based samples of people with ABI were recruited. Participants in Sample 1 (n=30) were concurrently evaluated on the OBS by two raters at Time 1. One of the raters readministered the OBS on a second occasion, one week later. Other validating scales were also administered. Sample 2 (n=28) consisted of clients of a statewide challenging behaviour service who were treated for challenging behaviours and were administered the OBS before treatment commenced and then again 4 months later.

Inter-rater reliability and stability: Inter-rater reliability was examined using the data from Sample 1. This was accomplished by correlating OBS indices (Cluster and Total Levels) from rater 1 with rater 2 at Time 1. Correlation coefficients were very strong for both the OBS Cluster (rs=.99, p <0.001) and OBS Total Levels (rs=.97, p< 0.001), indicating that the clinical descriptors can be used by different raters with a high degree of consistency. Test–re-test reliability was evaluated by correlating the OBS indices obtained by rater 1 at Time 1 and Time 2 (a period of 1 week). Correlation coefficients were again strong for OBS Cluster (rs=0.72, p< 0.001) and OBS Total Levels (rs=0.77, p< 0.001), indicating good stability of the OBS across a period of 1 week.

Convergent and divergent validity: Initial evidence of convergent and divergent validity was shown by a differential pattern of significant correlations with other measures. Moderate-to-strong coefficients (range 0.37–0.66) were observed between the OBS and other measures that had behavioural content (i.e. Mayo-Portland Adaptability Inventory, Current Behaviour Scale, Neurobehavioural Rating Scale–Revised). Divergent validity was shown by the lack of correlation between the OBS and the sub-scales of the same tools that did not measure challenging behaviour.

Responsiveness: Responsiveness was demonstrated in Sample 2. A significant decrease in OBS scores was found in the expected direction (fewer behavioural problems) over the 4-month period of behaviour management intervention. This improvement was confirmed by corroborating evidence from key informants.


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