  When data are missing due to at most one cause from some time to next time,
we can make sampling distribution inferences about the parameter of the data by
modeling the missing-data mechanism correctly. Proverbially, in case its
mechanism is missing at random (MAR), it can be ignored, but in case not
missing at random (NMAR), it can not be. There are no methods, however, to
analyze when missing of the data can occur because of several causes despite of
there being many such data in practice. Hence the aim of this paper is to
propose how to inference on such data. Concretely, we extend the missing-data
indicator from usual binary random vectors to discrete random vectors, define
missing-data mechanism for every causes and research ignorability of a mixture
of missing-data mechanisms such as "MAR & MAR" and "MAR & NMAR". In particular,
when the combination of mechanisms is "MAR & NMAR", generally the component of
MAR can not be ignored, but in special case, it can be.
