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44 Standardized Procedures for Personal Travel Surveys
It is recommended that
1. The definition of missing data indicated in Section 10.7 of the Technical Appendix be
adopted as a standard definition in transportation surveys;
2. The missing value index (MVI), shown below, be computed for all transportation data
sets; and
3. Values representing various levels of data quality be established based on experience with
the MVI over time.
The MVI is defined as
N I
xi,n
n=1 i =1
MVI = N I
xi ,n
n=1 i =1
where
MVI = Missing Value Index,
i,n =
x* {
1 if data item i of respondent n is missing
0 otherwise }
xi,n = {
1 if a response to variable i is applicable to respondent n
0 if a response is not applicable }
I = number of variables, and
N = number of respondents in data set.
2.7.8 Q-9: Adherence to Quality Standards and Guidelines
One of the ways to improve the quality of data is to have a checklist of actions that must be
performed or standards that must be met in each survey. Such a checklist is not currently
accepted or used in reporting on household and personal travel surveys. The reader is referred
to Section 10.8 of the Technical Appendix for further information.
Ten questions have been compiled to assess the quality of the survey process. It is recom-
mended that the following questions be answered for each future travel survey:
1. Has the survey agency an active quality control program in operation?
2. Is a senior, independent staff member responsible for quality control in the organization?
3. Have pretests been conducted?
4. Has a pilot survey (or surveys) been conducted?
5. Have validation surveys been conducted?
6. Have data reported by proxy been flagged to indicate they were obtained by proxy reporting?
7. Have data values obtained through imputation been flagged to indicate the nature of their
origin?
8. Has the survey report been prepared and submitted to the client?
9. Has a coding manual and other metadata that accompanies the data been prepared and
submitted to the client?
10. Have the survey data been adequately archived in a safe, accessible, and well-recognized
data storage location?
Answers in the affirmative are favorable; if each affirmative is allowed to count one point, then
a score out of 10 would indicate the level of adherence to principles of good survey practice. It is
recommended that this statistic be produced for all future travel surveys.
