standard_description: Understand the concept of a ratio and use ratio language to describe a ratio relationship between two quantities. For example, “The ratio of wings to beaks in the bird house at the zoo was 2:1, because for every 2 wings there was 1 beak.” “For every vote candidate A received, candidate C received nearly three votes.”
problem_activity: Task
A student interested in comparing the effect of different types of music on short-term memory conducted the following study:  80 volunteers were randomly assigned to one of two groups.  The first group was given five minutes to memorize a list of words while listening to rap music.  The second group was given the same task while listening to classical music.  The number of words correctly recalled by each individual was then measured, and the results for the two groups were compared.
Is this an experiment or an observational study?  Justify your answer.
In the context of this study, explain why it is important that the subjects were randomly assigned to the two experimental groups (rap music and classical music).


aligns: no