Dear Laaksonen,
The term MAR was carefully selected more than a quarter century ago so as
not to conflict with imprecise existing uses of the term in the
statistical literature dealing with missing data in experimental design,
MLE, etc. going back nearly half a century earlier. It may not be perfect
but it has a well defined mathematical meaning, which was accepted by the
editorial board of Biometrika of that time. "Unbiased" can also be viewed
as confusing, and we could try to redefine it to be "expectation unbiased"
versus "median unbiased" or the even more appealing "posterior unbiased"
etc., but that effort doesn't seem that fruitful. Or even closer, the
term "randomized" experiment could be viewed as confusing because it may
suggest to some no blocking, etc. -- i.e., a completely randomized
experiment. So maybe we should introduce the concept of the
"conditionally" randomized experiment?? I think it is best to accept
accepted definitions. Agree?
Best wishes, Don
On 29 Mar 2001, Laaksonen Seppo wrote:
> I do not like about the term MAR, missing at random. Of course, when
> it has been defined, there are no problems. But the direct
> interpretation of that term is confusing, since missingness is not
> random in this case but conditionally in some sense. The term should
> be something like missing at random conditionally (MARC) or MAR
> according to covariates. I am not fully satisfied to those terms. What
> do you prefer?
>
> Best regards
> Seppo Laaksonen
>
>
>
