either arm??

Please advise what “either arm” means in the sentence below.

(1) The Principal Investigator or Clinical Investigator shall obtain informed consent from potential subjects and perform the examinations necessary to assess eligibility.
(2) The Clinical Investigator shall make the necessary entries in the Case Registration Form and send it to the Data Center by fax.
(3) The Data Center shall decide if a subject is eligible based on the description in the Case Registration Form, and randomize the subject to either arm if the subject is judged to be eligible. Either the Case Registration Confirmation Form or the Ineligibility Announcement will be faxed to the Clinical Investigator, informing him/her of the results of the eligibility decision and randomization procedure.

I need to translate this into Japanese.

Thank you.

I believe the ‘arm’ could be described as “a part of an organization that deals with a particular subject or activity; the retailing arm of the business; an arm of the Justice Department” /Macmillan/

Dealing with your sentence, the Data Centre choses things in a random way and sends them to any of its (two) arms provided the subject is considered eligible.
That’s how I read it.

Thank you!

I thinks this “arm” means kind of group for investigation.
Is this correct?

It could refer to any part of an organization; if you have more context you could judge where it fits better. With no context, a ‘group for investigation’ suits well I think.

‘Either arm’ seems an odd choice in that case.
What is this assessing eligibility for?

The whole text seems to me deliberately over-complicated. Though I didn’t manage to come up with anything more meaningful.
Rendering it into Japan?..

Not so much ‘deliberately over-complicated’ as typical legal jargon, I think.

‘randomize the subject to either arm’ definitely needs improvement though.
“assign the subject randomly to one of two departments”