A pool store owner wants to determine the effect of algaecide brands on the treatment of pool water with algae. He adds a different brand of algaecide to each of three pools with similar algae levels. He measures the algae level in each pool after treatment.
Randomized or Obervational?

Randomized

Explanation:

Observational Studies and Randomized Trials are two ideal ways of determining the outcome of certain tests.

In the Observational course the study is conducted in a true to life scenario and the result of what happens is recorded. Meanwhile, in the Randomized  Trial there purposefully placed conditions that are ideal and these are evaluated after specific interventions.

Since the pool manager did not let different  pools grow algae at will before putting in the chemical this study would not be considered observational. Instead he set up three different pools of the same size with the similar amount of contaminants and then tested the algaecide. This classifies this as a Randomized Trial.