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.
Usually when both prescription and nonprescription versions of a drug are sold, the prescription version is a higher dose. Adding to the confusion is prescription-only Nexium, a slightly different version that's billed as next-generation Prilosec and advertises as today's purple pill..