Should postal epidemiological studies stop doing third mailings?: Examination of response bias in a health survey of women in the UK

Abstract

Objectives: To determine whether the three mailings routinely used by researchers for epidemiological surveys are useful and appropriate, by comparing social characteristics and selected disease histories to find out if there are differences between individuals responding at different times. Methods: Social characteristics and selected disease histories of 11,797 British women still under general practitioner observation in the Royal College of General Practitioners' Oral Contraception Study were compared. The women aged 40-78 at December 1992 were sent health survey questionnaires via their general practitioners between November 1994 and July 1995. Results: Significant differences in the ch..