From: Area-aggregated assessments of perceived environmental attributes may overcome single-source bias in studies of green environments and health: results from a cross-sectional survey in southern Sweden
Objective assessments using GIS
Absent
Present
Self-assessments
a0
a1
b0
b1
Total
n0
n1
Sensitivity = True positive self-assessment = b1/n1
Specificity = True negative self-assessment = a0/n0