please help: chemistry
Shawn wants to determine if there is a relationship between room color and sleep.Based on his research, Shawn makes an educated guess that people fall asleep more quickly in a room painted blue than in a room painted yellow. He asks several people which color they like better, yellow or blue, and uses their responses to see if his educated guess was correct. What is missing from Shawn's scientific investigation?

Question

please help: chemistry
Shawn wants to determine if there is a relationship between room color and sleep.Based on his research, Shawn makes an educated guess that people fall asleep more quickly in a room painted blue than in a room painted yellow. He asks several people which color they like better, yellow or blue, and uses their responses to see if his educated guess was correct. What is missing from Shawn's scientific investigation?