In the following we will refer to the year field as field one; the
month field as field two, and the day field as field three. One of the first problems we have not
addressed as yet is a suitable way to refer to the subscripts Rk and Ck. Each k is a different
combination of agreement, disagreement, and missing. It is customary to refer to such combinations
as vectors. A vector in this sense is simply a single dimensioned array of values. In this case the
values are ternary, i.e., there are three possible [Agreement, Disagreement, Missing]. We need to
adjust the presence values when the data is not missing. For three fields there are eight combinations
(vectors) when data is either present or absent: 
1 = [ ], i.e., no fields present, 2 = [ 1 ], i.e., only
year present, 3 = [ 2 ], i.e., only month present, 4 = [ 3 ], i.e., only day present, 5 = [ 1, 2 ], i.e., year
and month present, 6 = [ 1, 3 ], i.e., year and day present, 7 = [ 2, 3 ], i.e., month and day present,
8 = [ 1, 2, 3 ], i.e., year, month and day all present. As pointed out in 5-2.4, there is a presence
dependence, so the adjusted presence on only four of these is non-zero: 1 = [ ], i.e., no fields
present, 2 = [ 1 ], i.e., only year present, 5 = [ 1, 2 ], i.e., year and month present, and 8 = [ 1, 2,
3 ], i.e., all three date fields present. We also explained in 5-2.4, that when we compare two
records their various comparisons are then grouped into four cases; these cases we then refer to as
ap0, ap1, ap2, ap3. Table 1 includes these values as some of the raw data needed before beginning
probability calculations.
| Case |
Comparisons |
Adjusted Presence Eq. (4.1) |
Value |
| 0 |
1:1 1:2 1:5 1:8 |
ap0 = 1 – p12 |
1.0000 – 0.0119 = 0.9881 |
| 1 |
2:2 2:5 2:8 |
ap1 = p12 - p22 |
0.0119 – 0.0087 = 0.0032 |
| 2 |
5:5 5:8 |
ap2 = p22 – p32 |
0.0087 – 0.0082 = 0.0005 |
| 3 |
8:8 |
ap3 = p32 |
0.0082 |
| Reliability |
Coincidence |
| Agreement |
Disagreement |
Agreement |
Disagreement |
| r1 = 0.9506 |
1 – r1 = 0.0494 |
c1 = 0.0040 |
1 – c1 = 0.9960 |
| r2 = 0.9063 |
1 – r2 = 0.0437 |
c2 = 0.0178 |
1 – c2 = 0.9822 |
| r3= 0.8525 |
1 – r3 = 0.1475 |
c3 = 0.0326 |
1 – c3 = 0.9674 |
Table 1 — Preliminary Calculations
