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Table 6 Spearman’s rank correlations between measures of the accessibility of hospitals by aggregation method

From: The approaches to measuring the potential spatial access to urban health services revisited: distance types and aggregation-error issues

Accessibility measure Aggregation method Accessibility measures using Euclidean distance Accessibility measures using shortest network time (on foot)
CTCa WDAb WBLc CTCa WDAb WBLc
Minimum distance CTCa     
WDAb 0.994   0.992  
WBL1c 0.992 0.999 0.988 0.997
WBL2d 0.991 0.998 0.999 0.988 0.997 0.999
Average distance to all hospitals CTCa     
WDAb 0.999   0.999  
WBL1c 0.999 1.000 0.999 1.000
WBL2d 0.999 1.000 1.000 0.999 1.000 1.000
Average distance to three closest hospitals CTCa     
WDAb 0.998   0.997  
WBL1c 0.998 1.000 0.995 0.999
WBL2d 0.997 1.000 1.000 0.995 0.999 1.000
Average distance to five closest hospitals CTCa     
WDAb 0.999   0.998  
WBL1c 0.998 1.000 0.998 1.000
WBL2d 0.998 1.000 1.000 0.998 0.999 1.000
Number of hospitals within 500 m or 10 min CTCa    0.792 0.749
WDAb 0.753   0.792 0.935
WBL1c 0.716 0.940 0.749 0.935
WBL2d 0.704 0.923 0.985 0.740 0.921 0.962
Number of hospitals within 1000 m or 20 min CTCa     
WDAb 0.856   0.899  
WBL1c 0.819 0.954 0.875 0.967
WBL2d 0.809 0.942 0.984 0.878 0.963 0.985
Number of hospitals within 2000 m or 30 min CTCa     
WDAb 0.956   0.950  
WBL1c 0.950 0.992 0.940 0.983
WBL2d 0.949 0.991 0.998 0.935 0.982 0.994
Potential gravity model (friction parameter = 1) CTCa     
WDAb 0.995   0.996  
WBL1c 0.996 0.999 0.995 0.999
WBL2d 0.995 0.999 1.000 0.995 0.999 0.999
Potential gravity model (friction parameter = 1.5) CTCa     
WDAb 0.988   0.980  
WBL1c 0.989 0.998 0.975 0.993
WBL2d 0.988 0.997 0.998 0.981 0.995 0.996
Potential gravity model (friction parameter = 2) CTCa     
WDAb 0.972   0.952  
WBL1c 0.979 0.990 0.931 0.960
WBL2d 0.981 0.986 0.995 0.962 0.984 0.974
Two-step floating catchment area (2000 m or 30 min) CTCa 0.977 0.976   
WDAb 0.977 0.996 0.883  
WBL1c 0.976 0.996 0.863 0.976
WBL2d 0.976 0.996 0.999 0.864 0.978 0.992
Enhanced two-step floating catchment area with a slow step-decay function CTCa     
WDAb 0.918   0.908  
WBL1c 0.908 0.986 0.897 0.976
WBL2d 0.908 0.986 0.997 0.889 0.972 0.991
Enhanced two-step floating catchment area with a fast step-decay function CTCa     
WDAb 0.916   0.905  
WBL1c 0.906 0.986 0.894 0.975
WBL2d 0.907 0.986 0.997 0.887 0.971 0.991
Enhanced two-step floating catchment area with a gradient function CTCa     
WDAb 0.917   0.907  
WBL1c 0.908 0.987 0.895 0.975
WBL2d 0.909 0.987 0.997 0.887 0.972 0.991
  1. aAggregation method based on census tract centroid (the least accurate method)
  2. bAggregation method based on the population-weighted mean of the accessibility measure for dissemination areas within census tracts
  3. cAggregation method based on the population-weighted mean of the accessibility measure for blocks within census tracts
  4. dAggregation method based on the population-weighted mean of the accessibility measure for block centroids (adjusted with the land use map) within census tracts (the most accurate method)