Table 5.

Complete case bootstrap model selection results for the outcome measure persistent pain intensity

	most frequently selected models					rank
Predictors	1	2	3	4	5	B	CCA
longer duration of complaints	X	X	X	X	X	1	3
concomitant lower back pain	X	X	X	X	X	2	2
both shoulders afflicted	X	X	-	X	X	3	4
concomitant upper extremity pain	X	X	X	-	-	4	6
shoulder complaints in the past year	X	-	X	X	-	5	-
sporting injury*						-	1
inability to perform daily activities*						-	5
sporting activities*						-	7
higher physical workload*						-	8
Count	120	96	58	47	37
%	24.0	19.2	11.6	9.4	7.4

*             - predictors that appeared in ≥ 40% in the first step of the of the bootstrap model selection are not used in the second step in model selection

rank        - the order of appearance of predictors in the derived models arranged by their predictive ability (regression coefficient estimates)

B            - the complete case date based bootstrap selected model (i.e. the most frequently occurring combination of predictors in 500 replicate data sets of the second bootstrap model selection step)

CCA        - the complete case data based model derived without additional bootstrap did not occur in the bootstrap model selection since some of the included predictors occurred ≥ 40% in the first selection step

Count     - the number of times the model was selected in the 500 replicate data sets of the second bootstrap model selection step