Learning Objectives
- Define cross-sectional time frame, provide an example of a cross-sectional time frame, and outline some of the drawbacks of cross-sectional research.
- Describe the various types of longitudinal time-dimensions.
Cross-Sectional Studies
In terms of time, there are two main types of studies cross-sectional and longitudinal. Cross-sectional studies are those that are administered at just one point in time. These offer researchers a sort of snapshot in time and give us an idea about how things are for our respondents at the particular point in time that the study is administered. My own study of older workers mentioned previously is an example of a cross-sectional study. I administered the survey at just one time.
Another example of a cross-sectional sstudy comes from Aniko Kezdy and colleagues’ study (Kezdy, Martos, Boland, & Horvath-Szabo, 2011)Kezdy, A., Martos, T., Boland, V., & Horvath-Szabo, K. (2011). Religious doubts and mental health in adolescence and young adulthood: The association with religious attitudes. Journal of Adolescence, 34, 39–47. of the association between religious attitudes, religious beliefs, and mental health among students in Hungary. These researchers administered a single, one-time-only, cross-sectional survey to a convenience sample of 403 high school and college students. The survey focused on how religious attitudes impact various aspects of one’s life and health. The researchers found from analysis of their cross-sectional data that anxiety and depression were highest among those who had both strong religious beliefs and also some doubts about religion. Yet another recent example of cross-sectional survey research can be seen in Bateman and colleagues’ study (Bateman, Pike, & Butler, 2011) of how the perceived publicness of social networking sites influences users’ self-disclosures.Bateman, P. J., Pike, J. C., & Butler, B. S. (2011). To disclose or not: Publicness in social networking sites. Information Technology & People, 24, 78–100. These researchers administered an online survey to undergraduate and graduate business students. They found that even though revealing information about oneself is viewed as key to realizing many of the benefits of social networking sites, respondents were less willing to disclose information about themselves as their perceptions of a social networking site’s publicness rose. That is, there was a negative relationship between perceived publicness of a social networking site and plans to self-disclose on the site.
One problem with cross-sectional studies is that the events, opinions, behaviors, and other phenomena that such studies are designed to assess don’t generally remain stagnant. Thus generalizing from a cross-sectional study about the way things are can be tricky; perhaps you can say something about the way things were in the moment that you administered your study, but it is difficult to know whether things remained that way for long after you administered your study. Think, for example, about how Americans might have responded if administered a study asking for their opinions on terrorism on September 10, 2001. Now imagine how responses to the same set of questions might differ were they administered on September 12, 2001. The point is not that cross-sectional studies are useless; they have many important uses. But researchers must remember what they have captured by administering a cross-sectional study; that is, as previously noted, a snapshot of life as it was at the time that the study was administered.
One way to overcome this sometimes problematic aspect of cross-sectional studies is to administer a longitudinal study/ Longitudinal studies are those that enable a researcher to make observations over some extended period of time. There are several types of longitudinal studies, including trend, panel, and cohort studies.
Longitudinal Studies
The first type of longitudinal study is called a trend study. The main focus of a trend study is, perhaps not surprisingly, trends. Researchers conducting trend studies are interested in how people’s inclinations change over time. The Gallup opinion polls are an excellent example of trend studies. You can read more about Gallup on their website: http://www.gallup.com/Home.aspx. To learn about how public opinion changes over time, Gallup administers the same questions to people at different points in time. For example, for several years Gallup has polled Americans to find out what they think about gas prices (something many of us happen to have opinions about). One thing we’ve learned from Gallup’s polling is that price increases in gasoline caused financial hardship for 67% of respondents in 2011, up from 40% in the year 2000. Gallup’s findings about trends in opinions about gas prices have also taught us that whereas just 34% of people in early 2000 thought the current rise in gas prices was permanent, 54% of people in 2011 believed the rise to be permanent. Thus through Gallup’s use of trend study time dimension, we’ve learned that Americans seem to feel generally less optimistic about the price of gas these days than they did 10 or so years ago. It should be noted that in a trend study, the same people are probably not answering the researcher’s questions each year. Because the interest here is in trends, not specific people, as long as the researcher’s sample is representative of whatever population he or she wishes to describe trends for, it isn’t important that the same people participate each time.
Next are panel studies. Unlike in a trend study, in a panel study the same people do participate in the study each time it is administered. As you might imagine, panel studies can be difficult and costly. Imagine trying to administer a study to the same 100 people every year for, say, 5 years in a row. Keeping track of where people live, when they move, and when they die takes resources that researchers often don’t have. When they do, however, the results can be quite powerful. The Youth Development Study (YDS), administered from the University of Minnesota, offers an excellent example of a panel study. You can read more about the Youth Development Study at its website: http://www.soc.umn.edu/research/yds. Since 1988, YDS researchers have administered an annual survey to the same 1,000 people. Study participants were in ninth grade when the study began, and they are now in their thirties. Several hundred papers, articles, and books have been written using data from the YDS. One of the major lessons learned from this panel study is that work has a largely positive impact on young people (Mortimer, 2003).Mortimer, J. T. (2003). Working and growing up in America. Cambridge, MA: Harvard University Press. Contrary to popular beliefs about the impact of work on adolescents’ performance in school and transition to adulthood, work in fact increases confidence, enhances academic success, and prepares students for success in their future careers. Without this panel study, we may not be aware of the positive impact that working can have on young people.
Another type of longitudinal study is a cohort study. In a cohort study, a researcher identifies some category of people that are of interest and then regularly studies people who fall into that category. The same people don’t necessarily participate from year to year, but all participants must meet whatever categorical criteria fulfill the researcher’s primary interest. Common cohorts that may be of interest to researchers include people of particular generations or those who were born around the same time period, graduating classes, people who began work in a given industry at the same time, or perhaps people who have some specific life experience in common. An example of this sort of research can be seen in Christine Percheski’s work (2008)Percheski, C. (2008). Opting out? Cohort differences in professional women’s employment rates from 1960 to 2005. American Sociological Review, 73, 497–517. on cohort differences in women’s employment. Percheski compared women’s employment rates across seven different generational cohorts, from Progressives born between 1906 and 1915 to Generation Xers born between 1966 and 1975. She found, among other patterns, that professional women’s labor force participation had increased across all cohorts. She also found that professional women with young children from Generation X had higher labor force participation rates than similar women from previous generations, concluding that mothers do not appear to be opting out of the workforce as some journalists have speculated (Belkin, 2003).Belkin, L. (2003, October 26). The opt-out revolution. New York Times, pp. 42–47, 58, 85–86.
All three types of longitudinal studies share the strength that they permit a researcher to make observations over time. This means that if whatever behavior or other phenomenon the researcher is interested in changes, either because of some world event or because people age, the researcher will be able to capture those changes. Table 3.1 summarizes each of the three types of longitudinal studiess.
Table 3:1 Types of Longitudinal Studies
| Sample type |
Description |
| Trend |
Researcher examines changes in trends over time; the same people do not participate in the study more than once. |
| Panel |
Researcher studies the exact same sample several times over a period of time. |
| Cohort |
Researcher identifies some category of people that are of interest and then regularly studies people who fall into that category. These are not the same people at each snapshot. |
In sum, when or with what frequency a study is administered will determine whether your study is cross-sectional or longitudinal. While longitudinal studies are certainly preferable in terms of their ability to track changes over time, the time and cost required to administer a longitudinal study can be prohibitive. As you may have guessed, the issues of time described here are not necessarily unique to research. Other methods of data collection can be cross-sectional or longitudinal—these are really matters of research design.
KEY TAKEAWAY
- Time is a factor in determining what type of researcher administers; cross-sectional studies are administered at one time, and longitudinal studies are administered over time.
