Using Tables from Part 3 of CTPP: A note of caution
To protect individual confidentiality, the Census Bureau introduced rounding and thresholds.
Rounding
For a discussion on rounding, please read www.fhwa.dot.gov/ctpp/sr0404.htm. To minimize the effects of rounding, we suggest replacing any cell value equal to 4 with 5.
Thresholds
Three unweighted observations were required for Tables 3-03 to 3-07. Small geography (eg. tract-tract, taz-taz) are severely impacted.
At small area geography (anything more detailed than state-place summary level) data from Tables 3-03, 3-04, 3-05, and 3-06 are severely affected, and should be used with caution. For example, the following table shows severe loss of worker counts when using table 3-06 for Pima County, AZ.
|
Summary Level |
Table 3-01 (Without Threholds) |
Table 3-06 (Thresholds) |
||
|---|---|---|---|---|
|
Workers |
Pairs |
Workers |
Pairs |
|
|
Tract-Tract |
357,695 |
13,320 |
264,146 |
3,179 |
|
Zone-Zone |
354,566 |
26,781 |
126,,218 |
4,644 |
