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. Author manuscript; available in PMC: 2017 May 1.
Published in final edited form as: Heart Lung. 2016 Apr 1;45(3):283–290. doi: 10.1016/j.hrtlng.2016.03.001

Table 3. Cystic fibrosis, step-wise regression models for predicting total exercise duration or peak exercise workload.

R2 Semi-partial R2 Intercept b β P-value
Total exercise duration (sec)
Step 1 (final step-wise model)
QI 0.63* - 204 78 0.79 <0.001
Peak exercise workload (watts)
Step 1
 HR 0.63* - -255 2.3 - <0.001
Step 2 (final step-wise model)
 HR 0.74* 0.39 -244 2.0 0.67 <0.001
 SVI - 0.35 - 1.0 0.36 0.01

Data presented as step-wise linear regressions. Variables entered the model upon reaching an alpha set at 0.15, whereas variables remained in the final model upon reaching an alpha set at <0.05. Independent variables used for entry into step-wise regressions were FVC, forced vital capacity (rest); FEV1, forced expiratory volume in 1-second (rest); VO2, oxygen uptake (peak exercise); HR, heart rate (peak exercise); QI, cardiac index (peak exercise); or SVI, stroke volume index (peak exercise). Dependent variables were total exercise duration or peak exercise workload. Coefficient of determination (R2) is for the overall model at each step. β, standardized slope. P-value = alpha value for each parameter in regression models.

*

p<0.05, for the model at each step.