Table 4

Sample size requirements

Attribute/levelExpected sample size required to estimate parameter by design type
Psychological intervention
 Home-based with telephone support290308
 Home-based with face-to-face support245251
 Group face-to-face in primary or community care370362
 Group face-to-face in secondary care227228
Information provided
 No information4141
 Printed leaflet126 596120 853
 Overview from a healthcare professional304321
 Overview from a healthcare professional plus printed leaflet8987
Format of the therapy manual and exercises
 Paper copy plus CD39 76839 841
 Paper copy plus DVD960924
 Paper copy plus website179190
 Paper copy plus smartphone application104100
 Additional cost to the National Health Service22
 Programme start2524