| Observation | (1) | (2) | (3) | (4) |
|---|---|---|---|---|
| K20 | K4 | X1+z1 | X2+z2 | |
| Y1 | + | − | ||
| Y2 | + | − | ||
| Y3 | + | − | ||
| Y4 | + | − | ||
| Y5 | + | − | ||
| Y6 | + | − |
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