Table 5 |
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|
Aggregation errors in measures of the accessibility of hospitals at the census tract level |
||||||||
|
Absolute difference between accessibility measure obtained from CTCa and WBlc aggregation methods |
Percentiles |
|||||||
|
Mean |
5% |
10% |
25% |
50% |
75% |
90% |
95% |
|
|
|
||||||||
|
Shortest network distance |
||||||||
|
Minimum network distance |
365.35 |
11.19 |
22.54 |
57.40 |
147.23 |
365.04 |
947.76 |
1,595.45 |
|
Average distance to 3 closest services |
284.19 |
5.88 |
12.07 |
32.04 |
102.51 |
276.01 |
719.27 |
1,250.98 |
|
Average distance to 5 closest services |
290.26 |
5.10 |
11.81 |
34.16 |
94.54 |
275.32 |
800.69 |
1,300.49 |
|
Average distance to all services |
309.02 |
3.44 |
7.42 |
26.94 |
89.12 |
275.50 |
869.61 |
1,470.33 |
|
Number of services within 500 metres |
0.04 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.06 |
0.34 |
|
Number of services within 1000 metres |
0.07 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.26 |
0.50 |
|
Number of services within 2000 metres |
0.14 |
0.00 |
0.00 |
0.00 |
0.00 |
0.15 |
0.47 |
0.77 |
|
Shortest time distance |
||||||||
|
Minimum time distance |
0.37 |
0.02 |
0.03 |
0.09 |
0.20 |
0.41 |
0.84 |
1.34 |
|
Average distance to 3 closest services |
0.31 |
0.01 |
0.02 |
0.06 |
0.15 |
0.34 |
0.73 |
1.11 |
|
Average distance to 5 closest services |
0.31 |
0.01 |
0.02 |
0.06 |
0.15 |
0.35 |
0.75 |
1.16 |
|
Average distance to all services |
0.32 |
0.02 |
0.03 |
0.06 |
0.15 |
0.37 |
0.73 |
1.22 |
|
Number of services within 10 minutes |
0.69 |
0.00 |
0.00 |
0.07 |
0.39 |
0.93 |
1.72 |
2.60 |
|
Number of services within 20 minutes |
0.76 |
0.00 |
0.00 |
0.00 |
0.25 |
0.71 |
1.98 |
3.20 |
|
Number of services within 30 minutes |
0.52 |
0.00 |
0.00 |
0.00 |
0.04 |
0.41 |
0.98 |
2.15 |
|
|
||||||||
|
Absolute difference between accessibility measure obtained from WDAb and WBlc aggregation methods |
Mean |
5% |
10% |
25% |
50% |
75% |
90% |
95% |
|
|
||||||||
|
Shortest network distance |
||||||||
|
Minimum network distance |
134.15 |
3.51 |
6.89 |
20.20 |
51.74 |
136.36 |
311.82 |
501.59 |
|
Average distance to 3 closest services |
118.06 |
2.14 |
4.50 |
16.10 |
46.43 |
126.23 |
275.19 |
413.62 |
|
Average distance to 5 closest services |
123.87 |
2.15 |
5.01 |
14.99 |
48.60 |
140.36 |
300.31 |
421.81 |
|
Average distance to all services |
157.70 |
1.95 |
4.05 |
17.45 |
66.96 |
240.45 |
360.42 |
473.07 |
|
Number of services within 500 metres |
0.02 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.03 |
0.12 |
|
Number of services within 1000 metres |
0.04 |
0.00 |
0.00 |
0.00 |
0.00 |
0.00 |
0.08 |
0.22 |
|
Number of services within 2000 metres |
0.08 |
0.00 |
0.00 |
0.00 |
0.00 |
0.05 |
0.22 |
0.40 |
|
Shortest time distance |
||||||||
|
Minimum time distance |
0.12 |
0.00 |
0.01 |
0.02 |
0.06 |
0.11 |
0.27 |
0.43 |
|
Average distance to 3 closest services |
0.10 |
0.00 |
0.01 |
0.02 |
0.05 |
0.10 |
0.23 |
0.39 |
|
Average distance to 5 closest services |
0.10 |
0.00 |
0.01 |
0.02 |
0.04 |
0.10 |
0.22 |
0.39 |
|
Average distance to all services |
0.10 |
0.00 |
0.01 |
0.02 |
0.04 |
0.10 |
0.22 |
0.39 |
|
Number of services within 10 minutes |
0.23 |
0.00 |
0.00 |
0.02 |
0.12 |
0.29 |
0.57 |
0.84 |
|
Number of services within 20 minutes |
0.22 |
0.00 |
0.00 |
0.00 |
0.06 |
0.20 |
0.44 |
0.85 |
|
Number of services within 30 minutes |
0.14 |
0.00 |
0.00 |
0.00 |
0.01 |
0.11 |
0.31 |
0.68 |
|
|
||||||||
|
a Aggregation method based on census tract centroid (the least accurate method). b Aggregation method based on the population-weighted mean of the accessibility measure for dissemination areas within census tracts. c Aggregation method based on the population-weighted mean of the accessibility measure for blocks within census tracts (the most accurate method). |
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|
Apparicio et al. International Journal of Health Geographics 2008 7:7 doi:10.1186/1476-072X-7-7 |
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