Marcos continued watching Algebra Nation teaching videos about Statistical Studies. He took notes and learned to identify population, sample, variable of interest, parameter, and statistic of interest. There are different ways to gather data: sample surveys, observational surveys, and experiments. An experiment applies treatment to a situation. The three principles of experimental design are Randomization, Replication, and Control. Marcos answered questions where he had to identify the type of situation, and identify any problems with the collection of data. He also had to determine whether or not a sampling method was biased or not.