Researches investigated the effect of listening to music by Mozart before taking an IQ test. Subjects were randomly assigned to one of three groups and would either listen to Mozart music, be told to relax, or be given no instructions. The sample mean IQ in the Mozart group was 119, in the relax group was 111, and in the silent group was 110. a. Is this an experiment or an observational study? b. If it is an experiment, is it randomized or block design? c. If it is an experiment, identify the explanatory and response variables