SAMPLE SIZE CALCULATION AND STATISTICS According to the unpublished data of Premature Baby Foundation of Taiwan and Bravura of National Health Insurance (2003-2004), the recent data showed that the combined incidence of NEC (≧stage 2) or death for preterm VLBW infants was about 25 % for level III neonatal center in Taiwan. Setting the α error at 0.05 and β error at 0.1; and an absolute reduction of the incidence of NEC or death by 50%, the number needed to verify our hypothesis was 203 for each arm.