Aresearcher is interested in whether the type of music a person listens to (classical, hip-hop) and the volume of music (low, high) impact how much money one spends at the grocery store. the researcher randomly assigns each participant to either the classical music or hip-hop music condition. then, each participant is exposed to the low volume and high volume conditions, with a rest in between and counterbalancing of the order of volume conditions. this is an example of a(n) design.