= Log risk ratio
{title2=$\ell=\log(p_1/p_0)$}
The logarithm of a <risk ratio> is zero at equal risks, negative when the first risk is smaller, and positive when it is larger. For independent binomial event counts $d_1,d_0$ from samples $n_1,n_0$, its usual delta-method <variance> estimate is $1/d_1-1/n_1+1/d_0-1/n_0$. This approximation requires nonzero counts; zero-event arms need another procedure. Log estimates are convenient for inverse-<variance> <meta-analysis>, and exponentiation returns to the risk-ratio scale.
Back to article page
