A sample of 100 LBC1936 questionnaires (containing family history, personality and social items) were checked against our records to ensure accuracy of data entry. We found insufficient errors (about 45) in the sample of 100 questionnaire entries to warrant a complete data entry check. There were 41 errors of entry in 34,500 cells (0.12%; 100 subjects each with 345 columns of data), and 7 cells with missing information. The main data entry errors were found in cells containing data from the IPIP and NEO sections of the questionnaires, where individual item responses coded as 1, 2, 3, 4, or 5 were sometimes discrepant by one point, e.g. a 4 instead of a 5. There were no systematic errors. All errors and discrepancies found were checked and amended on the SPSS database, and entered into a data log book.
