Of the 1479 enumerated women, 47 were not found at the address given on the population list, and 41 were not invited as the required sample size for their age group had been reached.
The research project is designed to include a minimum of 250 patients; however, all patients treated at the unit are invited to participate, so the sample size is expected to increase further over time.
Patients, identified by consecutive sampling, were invited to participate until the planned sample size of 70 patients per centre was reached.
Having excluded patients with implanted pacemakers or defibrillators, those unable to give informed consent, or patients in whom the general practitioner (GP) considered participation was inappropriate (eg, terminal illness), all other patients over 75 were invited to take part until the sample size had been achieved (ie, 1000 participants had been recruited).
To ensure we could randomise schools in one batch and recruit the required sample size, 14 schools were invited to participate; 12 agreed and were subsequently randomised.
Between October 6, 2011 and February 1 , 2012 31% of the 192,931 women who were invited to participate completed the questionnaire, yielding a sample size of 59,947 cohort members.
*The representativeness criterion was met when ≥80% of women eligible were invited and 80% agreed to participate, or when sample size >300 (1 point).
Two practices had issued NHSHC invitations to fewer than the maximum intended sample size at the time of study invitation, so no sampling was undertaken and all eligible patients from those practices were invited to participate.
Generation 100 is unique because of the large sample size, because the entire population is invited and because of the long intervention period.
The sampling was performed at 2 stages (district and county) only and further stratification into the kindergarten and preschool was not performed because we needed to invite all kindergartens and preschools to achieve the large sample size.
