Claims of 'no difference' or 'no effect' in Cochrane and other systematic reviews.

Estimates of treatment effects/differences derived from controlled comparisons are subject to uncertainty, both because of the quality of the data and the play of chance. Despite this, authors sometimes use statistical significance testing to make definitive statements that 'no difference exists between' treatments. A survey to assess abstracts of Cochrane reviews published in 2001/2002 identified unqualified claims of 'no difference' or 'no effect' in 259 (21.

Olanzapine for the prevention and treatment of cancer-related nausea and vomiting in adults.

Background: Olanzapine as an antiemetic represents a new use of an antipsychotic drug. People with cancer may experience nausea and vomiting whilst receiving chemotherapy or radiotherapy, or whilst in the palliative phase of illness.

Objectives: To assess the efficacy and safety of olanzapine when used as an antiemetic in the prevention and treatment of nausea and vomiting related to cancer in adults.