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52 Standardized Procedures for Personal Travel Surveys 4.2.3 E-6: Retention of Data on Incomplete Households Data on incomplete households have the potential to provide extremely useful information that can be used in analysis of survey results and to improve the quality of surveys in the future. With these data, it is possible to examine the design of certain questions that may result in premature terminations of interviews and information on the biases in non-respondents. Despite the appar- ent usefulness of such data, in many surveys it is destroyed after the full sample is obtained either because it is automatically done by CATI software or because of specific desires of survey firms or clients. Many agencies are ignorant of the value of partial data and will either not specify in the con- tract that such data should be turned over or may even specify that such data are to be destroyed. In addition to this, many agencies would not know what to do with such data if retained and need help in knowing how to make optimal use of it. Again, there was insufficient time in this project to develop standardized procedures on the retention of data on incomplete households. It is recommended that several tasks be performed in any future research. As a starting point, one needs to define what constitutes a partially com- plete household. This would not be difficult in light of the work done in this project to define a complete household (see Section 2.2.3). At a minimum, households could be classified into the following basic categories: 1. Refused recruitment; 2. Terminated recruitment prematurely; 3. Completed recruitment, but refused mail-out survey; 4. Completed recruitment, accepted mail-out survey, but refused diary completion or retrieval of diary data; 5. Partially completed diaries and related information; and 6. Completed all survey materials. There is also a need to determine whether all incomplete household records should be retained or only those meeting some minimum criterion of completion. To do this, one would need to demonstrate the potential uses of such data through analysis of incomplete records from a variety of surveys. This might include examining the questions at which surveys are terminated and the distribution of household characteristics for households that are partially complete and those that are fully complete. A few key areas for analysis should be recommended to help determine what specific data should be retained. In developing data retention standards, it may be necessary to specify modifications that need to be made to some commercial CATI software packages. While subsequent analysis may determine that there is no useful information to be gained from some par- tially complete surveys, it would be prudent to err on the side of keeping too much rather than too little data. With the current low costs for data storage and the small overheads resulting from increasing the overall size of data sets, there is no reason to try to minimize retention of data by throwing out such data as that on incomplete households. 4.2.4 E-7: Cross-Checks in Data Collection and Data Review In any survey, cross-checks should always be undertaken on data to ensure that results are mean- ingful and certain information is not contradictory. For example, a survey in California a few years ago reported a substantial proportion of school children, under the legal minimum age for hold- ing a driver's license in California, apparently driving alone to school. There are other problems to be avoided: almost every travel survey includes instances of people forgetting to report a trip back to home at the end of the day or failing to report an activity at home after the last trip of the day. Work trips by people who report that they are not workers are another common occurrence in sur- veys. Another problem in activity and time-use diaries arises when people do not include activities at a place between trip segments--for instance, waiting at a bus stop or parking a vehicle.