Patients with Chronic Obstruction Pulmonary Disease (COPD) Volunteered to Be

Multiple Choice

Patients with chronic obstruction pulmonary disease (COPD) volunteered to be tested for exhaled nitric oxide (eNO) while resting and after a 6 minute walk test. Each subject was measured under each condition, and the order of presentation (resting then walking or the other way around) was randomized. Researchers believe the eNO should be higher while walking than resting for COPD patients. The data are summarized in the table below. Assume each of the distributions of eNO - while walking, while resting, and the differences - is not heavily skewed.
-Can we conclude that walking causes increased eNO levels in the group to which the conclusion applies?

A) Yes, because the researchers used a random sample.
B) Yes, because we randomly assigned order in the study.
C) Yes, because this is paired data.
D) No.