Measuring Public Agendas. The public agenda has been measured in at least four ways. First, respondents are asked an open-ended question such as “What do you feel is the most important political issue to you personally?” or “What is the most important political issue in your community?” The phrasing of this question can elicit either the respondent’s intrapersonal agenda (as in the first example) or interpersonal agenda (the second example). A second method asks respondents to rate in importance the issues in a list compiled by the researcher. The third technique is a variation of this approach. Respondents are given a list of topics selected by the researcher and asked to rank-order them according to perceived importance. The fourth technique uses the paired-comparisons method. Each issue on a preselected list is paired with every other issue, and the respondent is asked to consider each pair and to identify the more important issue. When all the responses have been tabulated, the issues are ordered from the most important to the least important.
As with all measurement, each technique has its own advantages and disadvantages. The open-ended method gives respondents great freedom in nominating issues, but it favors those people who are better able to verbalize their thoughts. The closed-ended ranking and rating techniques make sure that all respondents have a common vocabulary, but they assume that each respondent is aware of all the public issues listed and restrict the respondent from expressing a personal point of view. The paired-comparisons method provides interval data, which allows for more sophisticated statistical techniques, but it takes longer to complete than the other methods, and this might be a problem in some forms of survey research.
Three important periods used in collecting the data for agenda-setting research are (1) the duration of the media agenda measurement period, (2) the time lag between measuring the media agenda and measuring the personal agenda, and (3) the duration of the audience agenda measurement. Unfortunately, there is little in the way of research or theory to guide the investigator in this area. To illustrate, Mullins (1977) studied media content for a week to determine the media agenda, but Gormley (1975) gathered media data for 4.5 months. Similarly, the time lag between media agenda measurement and audience agenda measurement has varied from no time at all (McLeod et al., 1974) to a lag of 5 months (Gormley, 1975). Wanta and Hu (1994a) discovered that different media have different optimum time lags. Television, for example, has a more immediate impact, whereas newspapers are more effective in the long term.
It is not surprising that the duration of the measurement period for audience agendas has also varied widely. Hilker (1976) collected a public agenda measure in a single day, whereas McLeod and colleagues (1974) took 4 weeks. Eyal, Winter, and DeGeorge (1981) suggested that methodological studies should be carried out to determine the optimal effect span or peak association period between the media emphasis and public emphasis. Winter and Eyal (1981), in an example of one of these methodological studies, found an optimal effect span of 6 weeks for agenda setting on the civil rights issue. Similarly, Salwen (1988) found that it took from 5 to 7 weeks of news media coverage of environmental issues before they became salient on the public’s agenda.
In a large-scale agenda-setting study of German television, Brosius and Kepplinger (1990) found that the nature of the issue had an impact on the time lag necessary to demonstrate an effect. For general issues such as environmental protection, a lag of a year or two might be appropriate. For issues raised in political campaigns, 4 to 6 weeks might be the appropriate lag. For a breaking event within an issue, such as the Chernobyl disaster, a lag of a week might be sufficient.
Agenda-setting researchers are now incorporating more complicated longitudinal analysis measures into their designs. Gonzenbach and McGavin (1997) for example, present descriptions of time series analysis and time series modeling and a discussion of nonlinear analysis techniques.
Several researchers have used the experimental technique to study the causal direction in agenda setting. For example, Heeter, Brown, Soffin, Stanley, & Salwen (1989) examined the agenda-setting effect of teletext. One group of subjects was instructed to abstain from all traditional news media for five consecutive days and instead spend 30 minutes each day with a teletext news service. The results indicated that a week’s worth of exposure did little to alter subjects’ agendas. The experimental method has also been employed to measure the impact of different message frames. Valentino, Buhr, and Beckmann (2001) manipulated the frame of a news story about a politician by creating one version in which an elected official’s policy decision was represented as a sincere choice to benefit constituents and another version in which the same decision was represented as a selfish effort to win votes in the next election. The frame that emphasized the vote-getting effort produced more negative reactions than did the sincere choice interpretation.