standard_description: Fluently add and subtract within 1000 using strategies and algorithms based on place value, properties of operations, and/or the relationship between addition and subtraction.
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