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Table 1 Study size to obtain 80% statistical power in the proposed screening interventions for different baseline rates for invasive cervical cancer incidence assuming various marginal effects, when α = 0.05 and intervention to control ratio 1:1

From: Alternative technologies in cervical cancer screening: a randomised evaluation trial

Invasive cervical cancer incidence per 105 woman-years1 RR Woman-years in follow-up (intervention group); 1-sided test Woman-years in follow-up (intervention group); 2-sided test
5 0.5 820,000 1,020,000
5 0.7 2,467,000 3,097,000
10 0.5 410,000 510,000
10 0.7 1,233,000 1,548,000
15 0.5 273,000 340,000
15 0.7 822,000 1,032,000
20 0.5 205,000 255,000
20 0.7 617,000 774,000
  1. Calculation assumes inclusion of all the ages within organised screening for cervical cancer.
  2. 1 In Finland the baseline rate for invasive cervical cancer incidence is approximately 5, in the combined European material from 10 to 20