Answer:
They should tested more people
Step-by-step explanation:
To conduct an experiment, they have to collect many data, repeating the experiment multiple time, design the study etc .
The method used in this scenario is wrong, the outcome of their experiment is based on one sample and the experiment was only conducted once with test of validity.
The result gotten this research may had been because of preference in their reading environment
Joe might like listening to music while he studied which gives him edge to performed well.
Before they can come to a conclusion, they have to involve many individuals in the study