My favorite polling organization, Pew Research, has reported that people have become more and more likely to have "cell phones only," with no landline phones. Here is a graph showing the percentage of American adults who have cell-phone only households:
Questions
a) This figure provides a good opportunity to interpret a graph. Study the figure carefully. The figure seems to be illustrating two main points--one about time, and one about age. What are these two points?
Here's another figure from the story:
b) This figure, as well, seems to be illustrating two main points. What are the two main takeaway messages from this figure? (Hint: One takeaway message is the same here as in Question a.)
Given the data presented in this figure, Pew Research reports that it will call a higher proportion of cell-phone only households this year. Here is a quote from their website:
To keep pace with this rapid trend, the Pew Research Center will increase the percentage of respondents interviewed on cellphones in its typical national telephone surveys to 65%; 35% of interviews will be conducted by landline. Last year, we increased the ratio to 60% cellphone, with 40% conducted on landline. Back in 2008, when we first started routinely including cellphones in our phone surveys, just one-fourth (25%) of all interviews were done by cellphone.
c) Remind yourself that external validity (through generalizable sampling techniques) is especially important for frequency claims. Give two or three examples of research questions that fit this kind of claim.
d) Explain why it is important for polling organizations to know which households are cell-phone only and which are not. What specific kinds of political and social questions might be especially affected by cell-phone only proportions, given the data presented above?
e) Here's an interesting question: How might an organization like Pew Research obtain an accurate estimate of the number of cell-phone only households in the first place? What kind of sample would you need to get this estimate? How would you contact this sample?
Finally, here's an interesting description from Pew Research, discussing whether it would be smart to conduct polls only on cell phones, not land lines:
The question naturally arises: Why not interview everyone on a cellphone? In fact, at least one major national survey is going to do just that. The Surveys of Consumers, conducted by the University of Michigan, will begin calling only cellphones this month.
But we are not ready to make that change just yet, for at least two reasons. One is that there remains a small share of the public that is not reachable by cellphone. In the newly released data from the National Center for Health Statistics, 7% of adults live in households with a landline phone but no wireless phone. In addition, some people with landlines and cellphones may turn their cellphones on only to make calls or when they are expecting to be called. If these kinds of people are demographically different from those who are more easily reached on a cellphone, then the resulting sample will be less representative of the full population.
Thanks, Pew Research, for your transparency!
