Measurements of water quality were taken a river downstream from an abandoned chemical dumpsite. Concentrations of a certain chemical were were obtained from 9 measurements taken at the surface of the water, 9 measurements taken at mid-depth of the water. And 9 measurements taken at the bottom of the water. What type of study was conducted, and what is the response variable of the study?

(a) An experiment was conducted, response variable is the connection of the chemical

(b) An experiment was conducted,response variable is the depth of the water

(c) A census was conducted, and the response variables is the depth of the water

(d) An observational study was conducted, and the response variable is the depth of the water

According to Oxford dictionary; an experiment is; "a scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact."

The aim of the entire study is to discover the concentration of a certain chemical at various depths of the river. This means that the entire procedure was undertaken for the purpose of discovery. Hence it is an experiment.

The independent variable here is the depth of the river while the response variable is the concentration of the chemical of interest at each depth.

A responding variable changes as changes are made in the independent variable. The variable that is manipulated in an experiment is the independent variable.