A chemical engineer conducts an experiment to determine the amount of hydrochloric acid necessary to neutralize 2 milliliters (ml) of a newly developed cleaning solution. The chemist prepares five 2-ml portions of the solution and adds a known concentration of hydrochloric acid to each. The amount of acid necessary to achieve neutrality of the solution is determined for each of the five portions.

a. Identify the experimental units for the study.
b. Identify the variable measured.
c. Describe the population of interest to the chemical engineer.
d. Describe the sample.