Self validating controls
A checklist was designed for completion during the home visit including exposures relating to the kitchen, stairs, use of infant equipment, and safe storage of medicines and household products.
One small study (n=64) investigating a range of home safety topics, found a fairly high degree of consistency between self-reported and observed practices.21 Another small study (n=30) of poison prevention practices found sensitivity, specificity and predictive value of self-reported possession, safe storage of, and exposure to substances varied between substances.22 It is of note that both studies took place within one city in England, and findings need confirmation from larger studies and with different populations.
This would enable a specificity of 80% to be estimated to within ±9.8%, assuming 80% of participants did not have the exposure.
Since sensitivity and specificity may vary between cases and controls, 80 cases and 80 controls were required across the four study centres.
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See: They can be used as the sole research instrument (eg, in descriptive epidemiological studies) or as just one tool within research, such as RCTs or case-control studies.3 Questionnaires have also been used by practitioners, for example, in order to identify those who may benefit from home safety interventions.4 However they are used, it is crucial that care is taken with planning, and that they are rigorously designed.5–9 A key issue in survey research is validity, and concerns have been raised that self-reported safety practices might overestimate safe behaviour.10 11 Measures with few false positives will be useful for practitioners for identifying those who may benefit from home safety interventions and for researchers, as high levels of specificity have been found to minimise bias in estimates of treatment effects in trials.12 More recently, different types of survey methods have been tested including face-to-face interviews, telephone interviews and researcher administered questionnaires; with considerable variation in their findings.13–20 It is important to note that these studies also varied in terms of topics covered; number of questions; timing of the observations in relation to the self-report and settings for the self-report.