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If anyone is going to argue this way, would it not be more appropriate to base the whole thing only on deaths? After all, we know that the children are dead. Then the probability of a death being a cot death is 394/4959 or 1 in 12.6, that of a homicide 14/4959 or 1 in 354. Petra Dr. Petra Leimich Lecturer in Statistics and Information and Communication Technology School of Computing University of Abertay Dundee Dundee e-mail: [log in to unmask] DD1 1HG phone: +44 (0)1382 308957 Scotland fax: +44 (0)1382 308627 -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: 12 November 1999 09:58 To: Allstat UK list Subject: Statistics and Justice Allan Reese has written about the case of the woman convicted of killing her two children, apparently partly on the basis of a statistical argument. I thought members might be interested in some data. In 1996, the most recent year for which data are available, there were 649,489 live births in E&W. There were 4,959 deaths in the first year of life, including 394 sudden infant deaths (SIDS or cot deaths) and 14 homicides. Thus the probability of a cot death is 1 in 649489/394 = 1,648. If deaths were independent, which they are not because there are familial risk factors, the risk that a fimily of two babies would have two cot deaths would be 1 in 1,648*1,648 = 2,715,904. Presumably some other adjustment was applied for social factors as the figure given in the press is said to apply to `well-to-do families'. But the same calculation for homicide gives a risk that that two baies will both be murdered as one in (649489/14)^2 = 2,152,224,291. If the first figure is relevant, so is the second. As Allan says, neither is relevant. Martin . Prof J M Bland Dept of Public Health Sciences St George's Hospital Medical School London SW17 0RE, UK Tel 0181-725 5492 email [log in to unmask] ----------------------------------------------------------------- This mail sent through SGHMS Webmail: https://webmail.sghms.ac.uk/ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%