I often use the American Community Survey (ACS) in conjuction with MAST to answer questions on the question-and-answer site Quora.com. Here is some additional information about how those answers are created.
The answers are derived from the 2014 ACS (American Community Survey) PUMS (Public Use Microdata Sample) file from the US Census Bureau. Tabulations are created by MAST (Multi-dimensional Analytical and Simulation Tool). Sometimes the free Android app “Gateway To MAST” is used, which allows anyone with an android device or kindle to create fairly simple MAST tabulations. After the original tabulations are produced, the spreadsheets are often manipulated by sorting, rearranging, calculating and charting in order to create a useful presentation.
Many tabulations from MAST have two sections:
1. An upper, household level section, that gives information about the households.
2. A lower, person level section that gives information about the people who live in the households.
Meanings of columns in the spreadsheet:
Wgtp: Weighted household count. Because the ACS is a sample, each household is weighted to indicate how many households in the US are represented by that particular household.
Pwgtp: Weighted person count. Because the ACS is a sample, each person is weighted to indicate how many people in the US are represented by that particular person.
LoVal/HiVal: Because the ACS is a weighted sample, the numbers are not expected to be 100% accurate. The Census Bureau has given us a facility to indicate how accurate the numbers are likely to be, and there is a 90% confidence that the actual number (for either Wgtp or Pwgtp) lies between the HiVal and LoVal. If LoVal is negative, that just means that the margin of error is larger than the count, which is common when the counts are small. It should be considered to be zero in these cases.
PL_Wgtp: Weighted household count at the person level. This tells you how many households the people (Pwgtp) on a particular line live in.
If you would like to try a scaled-down version of MAST for free, you are welcome to do so. (Scaled-down means up to 8 dimensions, 8 volumes, 2 levels, and the resulting tabulation must be no more than 300,000 characters for automated delivery. It can be larger than 300,000 characters, but I’ll have to manually email it when I get a chance to do so.)