Step-by-step explanation:
from the available data in this question,
1.
this population is applicable to those teenagers in the study who are aged 13 to 17 years and who own a smartphone
2.
from the question, this population is applicable to the the teenagers in the study within the age of 13 to 17 years who do not own a smartphone.
3. pew research conducted a sample survey and not a census to obtain their results. it would be illogical and not practical to conduct a census. A sample survey is better for this since it would cost less, save more time and also the members of the survey can easily be picked from the american teenage population.. a census would require data for the full population compared to sample survey which would only require a subgroup of the teenage population.