Agave is a plant that grows in Mexico and the southwestern U. S. Researchers at Penn State University conducted a study to see if a syrup made from the Agave nectar was effective at relieving cough in children. In this study the researchers recruited 80 children who went to an outpatient pediatric practice with a cough. The researchers randomly assigned the children to one of two groups (40 to each). One group received a grape flavored agave nectar and the other group received a placebo in the form of grape flavored water, which tasted identical.

The parents of the children were then asked to complete a survey on how frequently the child coughed that night. The parents were aware of whether the child received the agave or the placebo, but were instructed not to provide any information about this to their children. The researchers found that there was no statistically significant difference between the agave and placebo groups.

Identify the:

(1) experimental design,
(2) subjects
(3) explanatory variable, and
(4) response variable.