Does frequent use of acetaminophen lead to asthma-related complications among children? Excerpts from the abstract of a study published in The New England Journal of Medicine about this are given (Sheehan et al. 2016). Read them and then answer the questions that follow.

Methods: In a randomized, double-blind, parallel-group trial, we enrolled 300 children (age range, 12–59 months) with mild persistent asthmas and assigned them to receive either acetaminophen or ibuprofen when needed for the alleviation of fever or pain over the course of 48 weeks. The primary outcome was the number of asthma exacerbations that let to treatment with systemic glucocorticoids.

Results: The number of asthmas exacerbations did not differ significantly between the two groups, with a mean of 0.81 per participant with acetaminophen and 0.87 per participant in the ibuprofen group (p = 0.67).

a. Identify the treatment variable and the response variable.

b. Was this a controlled experiment or an observational study?

c. How does the p-value support the conclusion of the study?

d. Did this study use random sampling, random assignment, or both?