German cuisine widely available, but do not play an important role. Meat is usually braised; fried dishes also exist, but these recipes usually originate from France and Austria. Several cooking methods used to soften tough cuts have evolved into national specialties, including "Sauerbraten" (sour roast), involving marinating beef, horse meat or venison in a vinegar or wine vinegar mixture over several days. A long tradition of sausage-making exists in Germany; more than 1,500 different types of sausage () are made. Most "Wurst" is made with natural casings of pork, sheep or lamb intestines. Among the most popular and most common are "Bratwurst",
Time-varying covariate Time-varying covariate A time-varying covariate (also called time-dependent covariate) is a term used in statistics, particularly in survival analyses. It reflects the phenomenon that a covariate is not necessarily constant through the whole study. For instance, if one wishes to examine the link between area of residence and cancer, this would be complicated by the fact that study subjects move from one area to another. The area of residency could then be introduced in the statistical model as a time-varying covariate. In survival analysis, this would be done by splitting each study subject into several observations, one for each area