Dobbs J., Marsh A. (1982) Smoking among secondary schoolchildren, HMSO.
 Should any reader know anything of this early data, please get in touch with the author.
 At the time the Child and Adolescent Health Research Unit was based at the University of Edinburgh
 Schools have been encouraged to follow up on pupils who were absent on the day of completion.
 Sources: OPCS 1982-1986; ONS 1990-1998; NCSR 2000; SALSUS 2002-2013
 For the final user guide, we will add a table clearly stating the usable base sizes for 13 year old boys, 13 year old girls, 15 year old boys and 15 year old girls separately.
 For example, where two questions have been combined into a single question or where a similar question has been asked but in a different context.
 This is only noted for questions that are asked specifically in at least one wave.
 Particularly in relation to the impact of any changes in the questionnaire design or associated routing.
 This question has evolved over time, but should still allow meaningful comparisons over time.
 Bar two questions on solvent abuse asked in 1992 and 1994.
 The list of drugs asked about has evolved since 1998.
Email: Emma McCallum
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