|Data Source:||U.S. Census Bureau|
Universe: Workers 16 years and over
|Summary File 3 Technical Documentation -> Appendix C. Data Collection and Processing Procedures -> Glossary -> Imputation|
When information is missing or inconsistent, the Census Bureau uses a method called imputation to assign values. Imputation relies on the statistical principle of "homogeneity," or the tendency of households within a small geographic area to be similar in most characteristics. For example, the value of "rented" is likely to be imputed for a housing unit not reporting on owner/renter status in a neighborhood with multiunits or apartments where other respondents reported "rented" on the census questionnaire. In past censuses, when the occupancy status or the number of residents was not known for a housing unit, this information was imputed.
Internet Questionnaire Assistance (IQA)
An operation which allows respondents to use the Census Bureau's Internet site to (1) ask questions and receive answers about the census form, job opportunities, or the purpose of the census and (2) provide responses to the short form.
Interpolation frequently is used in calculating medians or quartiles based on interval data and in approximating standard errors from tables. Linear interpolation is used to estimate values of a function between two known values. Pareto interpolation is an alternative to linear interpolation. In Pareto interpolation, the median is derived by interpolating between the logarithms of the upper and lower income limits of the median category. It is used by the Census Bureau in calculating median income within intervals wider than $2,500.
|Summary File 3 Technical Documentation -> Appendix B. Definitons of Subject Characteristics -> Population Characteristics -> Journey to Work -> Travel Time to Work|
The data on travel time to work were derived from answers to long-form questionnaire Item 24b, which was asked of a sample of the population 15 years old and over. This question was asked of people who indicated in Question 21 that they worked at some time during the reference week and who reported in Question 23a that they worked outside their home. Travel time to work refers to the total number of minutes that it usually took the person to get from home to work each day during the reference week. The elapsed time includes time spent waiting for public transportation, picking up passengers in carpools, and time spent in other activities related to getting to work. (For more information, see "Reference Week.") Data were tabulated for workers 16 years old and over; that is, members of the armed forces and civilians who were at work during the reference week.
Aggregate travel time to work (minutes)
Aggregate travel time to work (minutes) is calculated by adding together all the number of minutes each worker traveled to work (one way) for specified travel times and/or means of transportation. Aggregate travel time to work is zero if the aggregate is zero, is rounded to 4 minutes if the actual aggregate is 1 to 7 minutes, and is rounded to the nearest multiple of 5 minutes for all other values (if the aggregate is not already evenly divisible by 5). (For more information, see "Aggregate" under "Derived Measures".)
Mean travel time to work (minutes)
Mean travel time to work is the average travel time in minutes that workers usually took to get from home to work (one way) during the reference week. This measure is obtained by dividing the total number of minutes taken to get from home to work by the number of workers 16 years old and over who did not work at home. The travel time includes time spent waiting for public transportation, picking up passengers in carpools, and time spent in other activities related to getting to work. Mean travel times of workers having specific characteristics also are computed. For example, the mean travel time of workers traveling 45 or more minutes is computed by dividing the aggregate travel time of workers whose travel time was 45 or more minutes by the number of workers whose travel time was 45 or more minutes. Mean travel time to work is rounded to the nearest tenth. (For more information on means, see "Derived Measures".)
|Summary File 3 Technical Documentation -> Appendix B. Definitons of Subject Characteristics -> Population Characteristics -> Work Status in 1999 -> Worker|
The terms "worker" and "work" appear in connection with several subjects: employment status, journey-to-work, class of worker, and work status in 1999. Their meaning varies and, therefore, should be determined by referring to the definition of the subject in which they appear. When used in the concepts "Workers in Family," "Workers in Family in 1999," and "Full-Time, Year-Round Workers," the term "worker" relates to the meaning of work defined for the "Work Status in 1999" subject.