Having a controlled group is very important.
Reason: If scientists did not have a controlled group then, they would have data for the test but they might know if the results changed or not. Scientists need a controlled group because the controlled group is like the original. They need the original group to help them know what improved or did not improve.
For example, if you were testing whether or not different types of music helps with studying, then you will need a group that does not listen to music so you can know if different types of music actually improve or just make studying worse.
Having a controlled group helps you know the difference between observations in a easier way. The controlled group is not something people should ignore. It might seem useless at first but, when a person starts to finish up their project or test then, they will understand why a controlled group is important. By the time they do, it might be too late so make sure you people use a controlled group(Especially in the Science Projects).
(Hope this helps : ) )
