Question

Funnel plot.

Hint:

Funnel plots are useful for detecting publication bias, but they should be interpreted with caution and in conjunction with other statistical tests.

Answer 1

A funnel plot is used to assess publication bias in a meta-analysis by plotting study effect sizes against their standard errors.
Step 1: Structure of a Funnel Plot:
1. X-axis: The effect sizes (such as odds ratios, mean differences) of the individual studies are plotted on the x-axis.
2. Y-axis: The standard errors of the effect estimates are plotted on the y-axis.
3. Symmetry: A symmetrical funnel shape suggests no significant publication bias, whereas an asymmetrical shape indicates potential bias.
Step 2: Interpretation of Funnel Plot:
1. Symmetry and Bias: If studies with smaller sample sizes (larger standard errors) tend to show larger effects, it suggests publication bias.
2. Visual Inspection: A symmetrical funnel plot indicates no significant bias, while an asymmetrical funnel plot suggests selective reporting or publication bias.