Dr. Jones wants to study the effects of playing Minecraft on fifth graders for one month. The hypothesis is that, the more the kids play the game, the greater the increase of visual spatial skills above baseline. Dr. Jones has four groups of 20 children randomly assigned. The first group is the control and does not play Minecraft. The second group is assigned to play for 15 minutes per day. The third group is to play for 30 minutes per day and the fourth group is to play for 60 minutes per day. All of the children chosen had not played Minecraft. All went through a one hour training period to play the game. Dr. Jones tests their visual spatial skills using a specific neuropsychological test. What is the independent variable? What is the dependent variable