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Fig. 3 | BMC Pulmonary Medicine

Fig. 3

From: Biological quality control for cardiopulmonary exercise testing in multicenter clinical trials

Fig. 3

Distribution of relative frequencies of paired differences from zero. Differences from zero for oxygen uptake (V̇O2), carbon dioxide output (V̇CO2), and minute ventilation (V̇E) at rest (ac), 20 W (df), and 70 W (gi). None of the variables show normal distribution when all tests are considered (Shapiro–Wilk test, P < 0.001). Test selection based on z ≤ 0.67 resulted in all data at each level of exercise (with the exception of V̇E at rest) being normally distributed (Shapiro–Wilk test, P > 0.05)

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