Table 2.
Time to complete ratings (in seconds).
| Two-category rating | Three-category rating | Four-category rating | Four-category rating (improved training) | Four-category rating (increased approval) | Four-category rating (Master Graders)a | |
| Mean time per HITs | 25.16 | 50.87 | 54.52 | 50.98 | 38.79 | 44.14 |
| 95% CI | 21.93-28.38 | 43.18-58.55 | 46.15-62.88 | 39.66-62.30 | 31.65-45.93 | 36.00-52.27 |
| Hourly wage, $ | 14.31 | 7.08 | 6.60 | 7.06 | 9.28 | 12.23 |
| Cost per image, $ | 1.10 | 1.10 | 1.10 | 1.10 | 1.10 | 1.95 |
aMaster graders received US $0.15 per image, plus a 30% Amazon commission for a total cost of US $0.195/image.