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.