A NOTE ON THE NUMBER OF PUNCHING ERRORS IN A CO‐ORDINATE INDEXING SYSTEM Available to Purchase

At the time of investigating the amount of noise in a peek‐a‐boo co‐ordinate indexing system, I produced some peripheral data concerning punching errors and would like to comment on the figure of 27 per cent which was quoted in the published results. This figure, however, was only a percentage of total noise and the actual percentage of punching errors was 089 per cent which was calculated on the basis that sixty‐six erroneously punched documents were retrieved out of a total retrieval figure in one hundred searches of 1,781 documents. Now this 089 per cent figure does not mean that in the punching of every hundred documents there was only approximately one error, what it does mean is that in one hundred searches only about one error per hundred retrieved documents was revealed.