A regression with two or more predictor variables is called a multiple. regression. (When we need to note the difference, a regression on a single predic-. tor is called a simple regression.) Weâd never try to find a regression by hand, and. even calculators arenât really up to the task.
Different jurisdictions have different definitions of what constitutes a prescription drug. Rx is often used as a short form for prescription drug in North America-a contraction of the Latin word  recipe  (an imperative form of recipere) meaning take.
Most of these answers are only partially correct or just PLAIN WRONG. If the Rx was written in July, it is still valid. Most Rx's are good for a year and NO Rx expires before 6 months unless the Dr. revokes it or no longer has a license to prescribe at the time you try to fill it. The length of time that a prescription is good for depends on the medication and the doctor.