Development of intestinal motility.

SIR,-Professor Brook and Dr Hindmarsh claim that children growing at a less than 3rd centile velocity carry a 97% chance of showing an abnormality on investigation.' In a leading article in the British Medical Journal in 1986 they wrote 'If a third centile velocity is chosen for immediate action the chances of investigating a normally growing child are only 3%5.2 The latter statement is capable of two interpretations. It could mean that 3% of normal children would be investigated, which is true. It could also be taken to mean that 3% of investigated children would be normal, which is not true, unless by chance. Only this second interpretation, however, fits with the assertion that 97% of investigated children would be abnormal. The percentage of children below the third centile who are abnormal is: