Dr. Fahad is interested in the effect of playing violent video games on aggression. Dr. Fahad studies this by manipulating the type of video game played and then measuring players' levels of aggressive thoughts on a survey. Group 1 plays "The Warrior Way," and Group 2 plays "Virtual Chess." To ensure that group differences in aggression results from playing different video games, Dr. Fahad should use which method?

Responses

stratified sampling

random selection

double-blind procedure

scatter plot

random assignment