616 Table 5. The numberof years needed to demonstrate at the 5 and 20% significance levels that there is a positive risk from occupational radiation exposure if the observed mean number of excess cancers are actually at the level we calculate. (Blanks signify > 10000 years.) These numbers maybe scaled to othersituations using eqn (5) Significance level age groups Byy 20%, I~ 16-25 3 545 26-35 ) 86-45 35 46-55 57 56-65 157 16-65 23 16-95 23 All 1575 34 18 31 107 17 od 5%, EX IN — — 79 241 36 135 64 216 232 899 4] Ss 79 88 AW) OO1L 130 Os 119 408 64 128 Cy 20% EX IN —_— 886 300 3o 136 2) 243 40 887 123 138 iG 301 1G All 367 20 ll 26 109 13 29 5%, EX TN _ 3381 49 135 24 8] 64 153 292 470 39 60 82 60 All 2 164 20%, EM IN _ — 188 19 90 9 243 10) 1113 416 149 51 314 112 23 V7 42 92 8 All —_ 3 6 23 133 10 8° 24 5%, Ex IN —_ —_ 10 37 18 35 87 $8 621 351 42 31 74 31 All — 20 23 86 506 37 Q2 Ex —_ 4Q 68 334 2372 161 284 “WD Ja punpssiay “FS Aso