Two-sided hypothesis test
= Two-sided hypothesis test
= Two-sided test
{synonym}
= Two-tailed test
{synonym}
A <two-sided test> detects departures in either direction from the <null hypothesis>, for example $\theta\ne\theta_0$. With a continuous symmetric null statistic centred at zero, its <p-value> is $P_0(|T|\ge|t_{\mathrm{obs}}|)=2P_0(T\ge|t_{\mathrm{obs}}|)$. This is the usual coefficient test printed by Gaussian regression summaries, unlike a directional one-sided comparison.