  In this work, we study the performance of two-sided EWMA charts for
monitoring double bounded processes using individual observations.
Specifically, the term double bounded refers to observations in the interval
(0, 1) and thus, these charts are suitable for monitoring rates, proportions
and percentages. There are several models that can be used to describe this
kind of data (and the respective processes, as well) such as the Beta
distribution, the Simplex distribution and the Unit Gamma distribution. For
each of these three models, we provide the statistical design and the
performance of the proposed EWMA charts. Also, apart from providing the
appropriate values for the design parameters of each chart, we investigate how
much the performance of the EWMA schemes is affected by using the values of
control limits which have not been calculated under the true model. Finally, an
illustrative example is also presented.
