If a target allocation of 40% has a corridor of 10%, is the allowable range then 30%-50%, or 36%-44%?
36-44
depends on what has been stated in the question. there have been questions where 30-50 has been correct. and there have been instances where the 36-44 was the right one. Depends on the wording … is it absolute 10% or it is a relative 10% of the “upper” or “lower” limit of the corridor thresholds. 10% absolute - then 30-50% 10% of the upper mark of the threshold -> then 40-4 to 40+4 -> 36-44
generally 30-50% is the correct corridor. I don’t think I’ve ever seen it as 36-44%, but that doesn’t mean it couldn’t be.
cpk123 is correct, there are two methods and which one you use depends on the wording of the question.