1. Parallax quality cut
Ratio = 3.4/0.9 = 3.78, which is below 5, so this source fails the quality cut.
| Criterion | Points |
|---|---|
| Correct ratio | 8 |
| Correct pass/fail | 7 |
Worked Solutions
2. Distance from parallax
d = 1000/6.2 = 161.3 pc.
| Criterion | Points |
|---|---|
| Correct formula | 5 |
| Correct value | 10 |
3. Magnitude cut
G = 13.2 < 14 passes; G = 15.8 > 14 fails.
| Criterion | Points |
|---|---|
| Correct classification of both | 15 |
4. Combined sample
Parallax/error: S1=20.7 (pass), S2=3.8 (fail), S3=45.5 (pass), S4=13.3 (pass), S5=2.5 (fail). Magnitude cut (G<14): S1 pass, S2 pass, S3 fail (15.5), S4 pass, S5 pass. Sources passing BOTH cuts: S1, S4.
| Criterion | Points |
|---|---|
| Correct parallax pass/fail for all five | 8 |
| Correct final retained sample | 7 |
Grading Notes
Award full marks for correct method, units, and a numeric result consistent with the arithmetic shown (allow reasonable rounding). Common partial-credit errors: omitting units, failing to combine uncertainties in quadrature, or overstating the confidence of a marginal (SNR 3–5) result.