Draft: add trials factor clarification

Description

Addresses #397

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analysis/index.rst

@@ -217,7 +217,12 @@ targets **significant** candidates from all online pipelines (**RAVEN**).
 We thus conservatively estimate a trial factor of **6** for :term:`stellar mass`
 :term:`CBC` searches and **3** for Burst searches. Similarly we have two
 independent :term:`SSM` :term:`CBC` searches (**GstLAL SSM** and **MBTA SSM**).
-Hence we use a trials factor of 2 for :term:`SSM` search alerts.
+Hence we use a trials factor of 2 for :term:`SSM` search alerts. The significance
+threshold in the section above can be found by taking the estimated rate of false alarms
+found just below and diving by the trials factors reported in this paragraph. As
+previously stated, the reported false alarm rates for events do not include this trial
+factor, but the significance threshold employed does. This keeps the estimated rates
+of false alarms the same regardless of the number of searches.
 
 The estimated rate of false alarms marked as **significant** is :math:`3.9
 \times 10^{-7}` Hz (one per month) for :term:`CBC` searches