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Table 1 The Horsfall and Barratt (H-B) quantitative ordinal scale showing the disease severity ranges, midpoints and interval sizes (Horsfall and Barratt 1945)

From: From visual estimates to fully automated sensor-based measurements of plant disease severity: status and challenges for improving accuracy

H-B categoryDisease severity rangeMidpointInterval size
1000
20+-31.53
33+-64.53
46+-129.06
512+-2518.513
625+-5037.525
750+-7562.525
875+-8881.513
988+-9491.06
1094+-9795.53
1197+-10098.53
121001000
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