If your latest round of research involves telephone research, you may want to ask what percentage of answers are being collected on cell phones versus land lines. The latest report from the National Health Interview Survey (NHIS) supports an ongoing upward trend in wireless-only households, with 106 million adults (44% of all adults) living in wireless-only households, and about 40 million children doing the same. The NHIS study shows some significant and interesting differences between wireless-only and landline households, differences that could have a real impact on your research.
Wireless-only households on the rise
More than 45 percent of homes in the U.S. just have wireless devices (no land lines), a 4.4 percent increase in the last year. The fact that it rose more than 4% versus prior year (second half of 2013 data) is statistically significant. The study shows that more than half of all adults ages 18-44 and more than half of children under the age of 18 live in wireless-only homes.
NHIS conducts in-person interviews throughout the year to gather research; their survey also includes questions on access to wireless devices within each household. Families were asked if there was “at least one phone inside your home that is currently working and is not a cell phone.” NHIS has been gathering this data since 2003. Families were also asked if anyone in the household had “access to a working cellular phone.” If yes, these families were flagged as “wireless families.” In turn, households as a whole were bucketed as a wireless households if there was no access to a landline and if one family within the household had a cellular device. More than 22,000 households were surveyed, add up to more than 41,000 adults.
Beware of bias
As with any research, it’s mission critical that the sample collected is representative of the target audience population. Many surveys use random digital dialing when conducting phone surveys, and these surveys often include wireless numbers. Conducting surveys focused only on landline phone numbers or only on wireless numbers presents an opportunity for biased results, especially when there are significant differences between wireless-only households and landline households.
Many researchers are also concerned about simply reaching those who have landline phones; these folks may not answer calls on their landline. They are more difficult to reach because, despite them having access to a landline, they still use their wireless devices for most or all calls. These people living in households with both wireless and landlines, but who receive most of their calls on their wireless devices have recently been categorized as “wireless mostly” households.
Ask the right questions before research begins
It’s important to know how your research is being performed, even at a high level. Unfortunately, there are some vendors who may do whichever telephone survey is most affordable, versus which is the best route to get the most representative data of the target audience. The decision to include or exclude wireless numbers in any survey requires considering many issues, including statistical differences and operational challenges. By asking these questions up front, you can be assured you’re working with the right vendor to get you the answers you need.
CFR is experienced at thinking through these issues to make sure you are able to receive the answers you need. If you are considering a telephone survey and would like to discuss your project with CFR, we would love to learn more. You can contact us here.