A researcher is interested in the relationship between caffeine consumption and activity level for elementary school children. A sample of 20 children is obtained and the children are separated into two roughly equivalent groups. The children in one group are given a drink containing 300 mg of caffeine and the other group gets a group with no caffeine. The researcher then records the level of activity for each child during a 30-minute session on the playground. Is this an experimentalor a correlational study? Explain your answer.