THE TIME-DIARY METHOD
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2. Media Usage: Differences in "tertiary" media use ("Was the television set (radio) on during that activity?") have been examined in Robinson (1990). 3. Environmental Tobacco Smoke (ETS) Exposure: Differences in exposure to secondhand tobacco smoke across activities have been analyzed in Robinson, Ott, and Switzer (1994). Figure 3.4 shows how this ETS exposure varies across the 24 hours of the day for both smokers and nonsmokers. Again, these aspects only suggest the facets of activities that remain unexplored in the usual diary studies–the time Americans spend in sickness and in health, dazed and confused, on-line or in love, or in ecstasy or quiet desperation. Indeed, it could be argued that this specific focus is an essential component of any proper investigation of an activity. Only so much of an activity's full context can be captured in the basic diary format usually employed; work, television, or personal care can take place at any point during the day and not be picked up in the diary. Unfortunately, there are limits to how many details respondents can be expected to report on a particular day. Once one asks more than two or three questions about each activity during the day, the reporting task becomes very burdensome, and the quality of respondent reporting can be expected to be adversely affected.
Computer File Formats Time-diary data are mainly analyzed in two types of formats, by activity (variable field) and by summary totals (fixed field). The activity file format is structured using the same activity-by-activity format as the raw diary entries described in Figure 3.3. It is described as a variable-field format because the number of activities is variable across respondents, some reporting 35 activities, others only 10–15 lines of activity descriptions. As shown in Figure 3.5A, the first line of the activity file (equivalent to the episode file, Chapter 2) contains the code for the first activity, the times it began and ended (in "military" time, e.g., 8:00 A.M. = 0800 and 8:00 P.M. = 2000), the duration of that activity (in minutes), the code for the secondary activity (if any), the code for the location of the activity, the code for social partners during the activity, and the code for any other feature of the activity (such as the enjoyment level during the activity or the presence of smokers) included in the diary format. The second line of the file contains the same information for the second activity in the diary.