To look more closely at Minnesota’s black population, the Star Tribune analyzed microdata from the U.S. Census Bureau’s American Community Survey. With assistance from the Minnesota Population Center at the University of Minnesota, we combined microdata from the 2011, 2012 and 2013 surveys in order to have a more statistically reliable sample. Microdata from the 2014 survey are not yet available.

Microdata make it possible to generate custom cross tabulations, averages or other calculations that the U.S. Census Bureau does not already publish. Primarily, we wanted to separate the black population into two groups: those born in the United States and those born in other countries. When looking at households, we identified households as foreign-born or U.S.-born based on the person who identified themselves as head of the household. As a result, households defined as foreign-born might contain children or other adults who were born in the United States, or vice versa.

We also used a statistical technique to test for “statistical significance” to determine if sampling error could be responsible for any of the differences between the two groups.

The American Community Survey (ACS) is an ongoing survey conducted by the U.S. Census Bureau, with questions on a variety of topics such as income, race, employment, educational attainment, commuting to work and housing. The survey goes out each year to about 3.5 million households nationwide (about 100,000 in Minnesota), with a response rate of about 97 percent. Data estimates generated from these surveys have a degree of uncertainty associated with them called sampling error. In general, the larger the sample, the smaller the level of sampling error.

For questions pertaining to income, the ACS asks respondents to include all types of wages, Social Security, pensions, welfare or other public assistance, unemployment compensation, Department of Veterans Affairs payments, child support/alimony, interest and dividends. Median household income is generated by grouping together these income totals for all individuals in a household. Income for people in group quarters, such as prisons, nursing homes, dormitories or military barracks, are not included in median household income calculations.

MARYJO WEBSTER