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 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. Here are a few guidelines for Rx's: The length of time that a prescription is good for depends on the medication and the doctor.