California Cancer Reporting System Standards, Volume III
Check Digit Calculation by the "Modified IBM 1022" Method
Calculations
1. Starting from the right, number the digits 1-7:
d7 d6 d5 d4 d3 d2 d1
2. Multiply each digit by the weighting factors 2-8 and add the products:
N = 8d7 + 7d6 + 6d5 +5d4 + 4d3 + 3d2 + 2d1
3. Divide the results by 11 and keep the remainder:
REM = N(mod11)
4. Subtract the remainder from 11 and use the result as the check digit if it is 1 through 9. If it is 10, the check digit is 0, and if it is 11, the check digit is 1.
Examples (correct original number)
a) |
1 x8 8 |
8 x7 56 |
3 x6 18 |
4 x5 20 |
3 x4 12 |
4 x3 12 |
9 x2 18 |
the sum N = 144
144/11 = 13 with remainder of 1
11 - 1 = 10
the check digit is 0.
b) 1 8 4 3 3 4 9 (transposition error)
the sum N = 142
142/11 = 12 with remainder of 10
11 - 10 = 1
the check digit is 1 and not 0.
c) 1 8 3 4 9 4 3 (skip transposition)
the sum N = 156
156/11 = 14 with a remainder of 2
11 - 2 = 9
the check digit is 9 and not 0.
d) 1 8 2 4 3 4 9 (mistaken digit)
the sum N = 138
138/11 = 12 with a remainder of 6
11 - 6 = 5
the check digit is 5 and not 0.