Interview Methodology
Interview Methodology
Interview Schedule & Fielding Periods
In the initial survey plan, respondents from each of the four Original Cohorts were to be interviewed yearly over a five-year period. Due to cost considerations, it was decided after the second survey of the Older Men to survey the two older groups (Older Men and Mature Women) biennially rather than annually. Due to their greater mobility, the younger groups were to continue to be interviewed annually. Because of the usefulness of these data and the relatively small sample attrition, a decision was made at the end of the first five-year period to continue the interviews for another five years. At this point, the interviewing pattern changed from a yearly personal interview to a 2-2-1 schedule; each respondent was contacted by phone approximately every two years, then again in person one year after the second phone interview. The 2-2-1 schedule was continued through 1981 for the Young Men and 1983 for the Older Men, when interviewing of both cohorts ceased. The Older Men or their proxies were then personally reinterviewed in 1990. Table 1 depicts the years in which each cohort was surveyed, the type of interview used, the fielding period, and the number and percent of respondents with completed interviews.
Table 1. Sample Sizes, Retention Rates, and Fielding Periods
User Notes
Although each of the personal interviews contains data of roughly the same degree of completeness, data gathered during the telephone interviews was not meant to update the longitudinal record of a respondent. Rather, the telephone interviews were intended to obtain a brief update of information on each respondent and to maintain sufficient contact so that the lengthier personal interview could be completed. The combination of fluctuating fielding periods and type of interview (i.e., personal or phone) may affect not only the probability of reinterview but also the reference periods of time-related questions.There is another source of inconsistency with respect to time references. A given year's survey instrument may use the previous calendar year as a reference period for some questions, while other questions will collect data for the year since last interview. Income data, for example, were often collected for the calendar year, corresponding to the time frame for a respondent's tax records; employment data were usually collected for the year since the last interview.