A Swim Coach Designs an Experiment to Determine If Children

A swim coach designs an experiment to determine if children who participate in group versus individual swim lessons have different swimming skills, on average. She randomly selects 20 children who have registered for swim lessons and randomly assigns them to group or individual swim lessons and collects data on the following: 1) type of swim lesson participated (two categories: group or individual) ; and 2) swimming skills (measured on a a scale from 0 to 200) . Her research question reads: Is there a mean difference in swimming skills for children who participate in individual versus group swimming lessons? Which of the following represents the INDEPENDENT variable?

A) 20 children
B) Random assignment
C) Swimming skills
D) Type of swim lesson