Answer:
in controlled experiment an independent variable is systematically manupulated and dependent variable is measured ; any extraneous variables are controlled
Answer:
a) Teens who use the Internet and phone after bedtime have a variety of sleep problems.
Explanation:
The STRICT (sleep time related information and communication technology) study performed in American adolescents showed that a high number of adolescents use their cell phone after bed time what results in insomnia, daytime sleepiness, later bedtimes and shorter sleep duration which are all sleep problems associated with the use of the cellphone and communication technology during sleep hours.
62% of the teens used their phone after bedtime, 56.7% texted/tweeted/messaged in bed, and 20.8% awoke to texts interrupting their sleep and the quality of it.
It is true but you dont have to be perfect in every detension in order to be healthy or well.
