Improve doc of estimated_sample_size
@@ -102,7 +102,7 @@ You may also find the description in our :ref:`API <modindex>` page.
*group_sequential* is a frequentist approach for early stopping:
* ``spending_function='obrien_fleming'``: Currently we support only Obrient-Fleming alpha spending function for the frequentist early stopping decision.
- * ``estimated_sample_size=None``: Sample size to be achieved towards the end of experiment.
+ * ``estimated_sample_size=None``: Sample size to be achieved towards the end of experiment. In other words, the actual size of data should be always smaller than estimated_sample_size.
* ``alpha=0.05``: Type-I error rate.
* ``cap=8``: Upper bound of the adapted z-score.
