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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.
