Meta-analyses IIIBMJ 2011; 342 doi: https://doi.org/10.1136/bmj.d244 (Published 26 January 2011) Cite this as: BMJ 2011;342:d244
- Philip Sedgwick, senior lecturer in medical statistics
- 1Section of Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
Previous questions described a meta-analysis of the effectiveness of parenteral corticosteroids for the relief of acute severe migraine headache in adults.1 2 Seven randomised controlled trials were identified in which single dose parenteral dexamethasone, administered alone or in combination with standard abortive therapy, was compared with placebo or any other standard treatment for acute migraine in adults. For each trial, the relative risk for recurrence of acute severe migraine headache in adults within 72 hours for the dexamethasone treatment arm compared with the placebo arm was obtained.3
The results of the meta-analysis were presented in a forest plot⇓. The test for statistical heterogeneity resulted in P=0.40.
Which of the following statements, if any, are true for the statistical test of heterogeneity?
a) Null hypothesis: homogeneity exists between the sample relative risks as estimates of the population parameter
b) Null hypothesis: heterogeneity exists between the sample relative risks as estimates of the population parameter
c) Alternative hypothesis: heterogeneity exists between the sample relative risks as estimates of the population parameter
d) Statistical heterogeneity existed between the seven trials in their estimates of the population relative risk. …