Error in calculation of statistical power.
D002543:Cerebral Hemorrhage / Q000628:therapy; D006801:Humans; D006849:Hydrocephalus / Q000517:prevention & control*; D007231:Infant, Newborn; D007235:Infant, Premature, Diseases / Q000517:prevention & control*; D013129:Spinal Puncture; D013223:Statistics as Topic