Berkowitz et al. (2018) conducted a trial of a home delivery of 10 meals per week for 12 weeks against usual diet and a healthy eating brochure. With reference to this cross‐over trial which of the following statements, if any, are true?

A. The cross‐over design is a ‘within subjects’ study design.

B. The sample is not prone to selection bias since subjects are compared to themselves.

C. The cross‐over trial is prone to a carry‐over effect.

D. The cross‐over trial would be expected to take longer than the equivalent parallel groups design.

E. The cross‐over trial design is more efficient than a comparable parallel groups design.