Dr. Alvarez wanted to see if he had discovered a new element, so he analyzed his new element and performed an experiment to determine the element's density, melting point, and boiling point. Then, he repeated his experiment four more times before reporting his results in a scientific journal. Dr. Casey read Dr. Alvarez's report. Wanting to verify Dr. Alvarez's data, Dr. Casey repeated Dr. Alvarez's experiment three times, compared his results with Dr. Alvarez's results, and reported his own results in a scientific journal. Which of the following is an example of replication?