We note that this correspondence is based in our case on a large sample of 927 individuals, and in the data referred to comprised a meta-analysis of many studies (Hein and Knight, 2008), so the data sets are sufficiently large that some reliance on them is reasonable.
For a case-study of a large sample of school children in Orange County, Florida (n = 104,865) the positional error of street geocoding was determined through comparison with a parcel database.
Furthermore, random selection of cases and a large sample size, both of which are critical to clinical studies involving many variables, are generally easier to achieve in a retrospective study than in a prospective study [ 6].
We carried out a questionnaire and case-note review study of a large sample of patients who had been repeatedly referred to medical specialists with MUS.
A recent case mix adjusted observational study of a large sample of ICU patients found that PAC use was associated with increased risk for mortality and resource use [ 28].
The cases, identified through intensive screening of a large sample of the Guanacaste population and among Guanacaste residents with invasive cancer presenting at regional and tertiary care hospitals, comprised an unbiased sample of Guanacaste women who developed ⩾CIN 2 during enrollment.
It analysed the effect of age at menarche, age at first full-term pregnancy, number of full-term pregnancies and number of spontaneous abortions both on the overall risk of breast cancer and on its pre- or postmenopausal onset, using the data on 1718 breast cancer cases, obtained from a large sample of around 100 000 French women participating in the E3N cohort study.
Previous case-control study on a large sample of blood donors has shown that RhD-positive heterozygotes are resistant to pathological effects of toxoplasmosis while RhD-positive homozygotes are only temporarily resistant: their psychomotor performance decreases with length of infection.
On the other hand, even a model with very good, though not perfect, calibration will fail the test in case of a sufficiently large sample.
It is important to add to this limitation the number of cases studied (a larger sample is advisable) and the evaluation of depressive symptoms at only two stages (a third evaluation might show how the symptoms would have evolved).
