Can choosing the type of music while studying make studying more effective? A researcher in higher education conducted a study to see if selecting the appropriate study music makes a person's learning more effective. One hundred volunteers were assigned a study room that blocked noise other than study music in their room. They were asked to complete an assessment. During the assessment, 20 volunteers had no music, 20 had classical music, 20 had R&B, and 20 had Jazz music. The researchers concluded that playing classical music allowed the volunteers to finish faster and have higher assessment scores. The above example describes: Convenience sampling method O random assignment O an experiment O an observational study