What does it mean "with control for differences in factors" in the sentence :
"Several studies used cross-sectional analyses to detect a positive relationship between the prevalence of gun ownership at the neighbourhood, county, regional or state level and homicide rates, with control for differences in factors associated with homicide (e.g., urbanization, race/ethnicity, unemployment, poverty, crime, and alcohol use)."
What did they do to those factors when they "control" them ?
The full report can be found here, if that helps for context: https://ajph.aphapublications.org/doi/full/10.2105/AJPH.2013.301409
Does that mean that they took in consideration all those factors (urbanization, race/ethnicity, poverty, etc.) in the method to minimize the impact those factors have in the results of the factor that matters the most to homicide rates in this study, in this case gun ownership? If so, how can it be done? An illustrative example is enough.