MS-2509

MS-2509

A clinical study is conducted, examining the effects of a new drug on elderly patients with arthritis. Arthritis patients are periodically telephoned by a researcher, Sarah, at regular intervals over a few months. Some of these patients are taking the new drug – Sarah knows which patients. Each time, she asks them some questions about their day-to-day functioning and general recovery.

Some of Sarah’s colleagues believe that she may be subconsciously reporting data in a way that favours the intended outcome of the study.

Which bias is this?