"Form value" is the value the answer option has in the data file. "Score value" is the value used in the algorithm when zygocity is calculated.
| Variable | Answer option | Form value | Score value |
| Drop | Like two drops of water | 1 | 1 |
| Like most siblings | 2 | -1 | |
| Don't know | 3 | 0 | |
| Stranger | Often | 1 | 1 |
| Occasionally | 2 | 0 | |
| Never | 3 | -1 | |
| Don't know | 4 | 0 | |
| Belief | Monozygotic | 1 | 1 |
| Dizygotic | 2 | -1 | |
| Don't know | 3 | 0 | |
| Eye, Voice & Dexter | Exactly the same | 1 | 1 |
| Almost like | 2 | 0 | |
| Different | 3 | -1 | |
| Don't know | 4 | 0 |
No answer option is used directly in the calculations, only the score values. In the following, it is these values (-1, 0 or 1) that are used in the algorithms. E.g. has Drop in the formula value 1 for a positive answer to whether the twins were equal to two drops of water.
zygo_recode(x, type)vector of numbers, either 1:3 or 1:4
Type of question to recode. Can either be 05, 06, 07 or 08, or drop, stranger, dexterity, voice, eye or belief.
return a vector with 0, -1 or 1.