Table 5.
Combinations of cases and readers having .80 power to detect a .05 AUC difference between spin-echo and cine MRI based on the Van Dyke et al [21] data. The pilot-study estimate of was negative. The left-hand-side results are for a planned study that has the same normal-to-abnormal ratio as the pilot study; the right-hand-side results are for a planned study that has equal numbers of normal and abnormal cases.
normal/abnormal ratio = 69/45 = 1.53 |
normal/abnormal ratio = 1 |
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Readers | Cases | Power | Cases | Power | Cases | Power | Cases | Power |
3 | 559 | 0.800 | 1898 | 0.800 | 374 | 0.800 | 1282 | 0.800 |
4 | 343 | 0.800 | 491 | 0.800 | 229 | 0.800 | 328 | 0.800 |
5 | 266 | 0.801 | 330 | 0.801 | 177 | 0.801 | 220 | 0.801 |
6 | 225 | 0.800 | 263 | 0.800 | 150 | 0.801 | 176 | 0.802 |
7 | 200 | 0.800 | 227 | 0.801 | 133 | 0.800 | 151 | 0.801 |
8 | 183 | 0.800 | 203 | 0.801 | 122 | 0.801 | 135 | 0.801 |
9 | 171 | 0.801 | 187 | 0.802 | 114 | 0.802 | 124 | 0.801 |
10 | 162 | 0.802 | 174 | 0.800 | 108 | 0.803 | 116 | 0.802 |
11 | 154 | 0.800 | 165 | 0.801 | 103 | 0.803 | 110 | 0.803 |
12 | 148 | 0.800 | 158 | 0.802 | 99 | 0.803 | 105 | 0.803 |
13 | 143 | 0.800 | 151 | 0.800 | 95 | 0.801 | 101 | 0.803 |
14 | 139 | 0.801 | 146 | 0.800 | 93 | 0.804 | 97 | 0.801 |
15 | 136 | 0.802 | 142 | 0.801 | 90 | 0.801 | 94 | 0.800 |