If true regional differences exist, applying the PM/Mortality C-R function to regions outside the study location could result in mis-estimation of effects in these regions.
Since we know that regional differences do not exist, functions can be safely applied to all regions.
mnli hypothesis: Since we know that regional differences do not exist, functions can be safely applied to all regions. premise: If true regional differences exist, applying the PM/Mortality C-R function to regions outside the study location could result in mis-estimation of effects in these regions.