A game developer for ShapeExplosion is really interested in how music affects peoples ability to complete the game. He wanted some to listen to soft music, others to listen to hard rock and others none at all. The game developer is also interested in how people interact with the software using a mouse or touch pad. What would an example of something that you could do to control variation? Have 10 people that are good at online games play with a touch pad and have 10 people who aren't good with online games use a mouse. Have 10 people in each treatment complete the game. Have everyone complete the game on the same computer. Randomly select 10 men and 10 women to complete each of the treatments.

When we do a scientific experiment, we create treatments to test the hypotheses that we established in the experiment. Each treatment will get the same number of repetitions, so that the evaluation of the treatments is done in an equal way providing a logical and correct result.

In the question above, we see that we are dealing with people playing while listening to soft music and using touch pad, people who play listening to soft music and using mouse, people who play listening to hard rock and using touch pad, people who play listening to hard rock and using mouse , and, people who are playing without listening to any music and without using a mouse or touch pad.

For the research evaluation to be done correctly and efficiently, it is necessary that each treatment has the same number of repetitions. That is, each treatment has the same number of people. Thus the correct thing to do would be to have 10 people in each treatment to complete the game.