Before you can interpret the numerical value of r, you need to determine if it was appropriate to calculate r to begin with. The Pearson correlation coefficient, r, describes the strength and direction of a linear relationship between two variables. The first step in exploring a linear relationship is to generate the scatterplot, which you learned about in the previous section.
New Smog Check Test Smog Check Program's Updated Test Technology Californians getting Smog Checks today may notice that the traditional tailpipe test used for many years has been replaced by a quicker, computer-based test for gasoline-powered cars model-year 2000 and newer, and for most diesel vehicles that are model-year 1998 and newer.
It's wise to have your vehicle tested several weeks prior to renewal to leave time for any necessary repairs. Emissions tests are valid for 12 months. Typically, your vehicle must be smog checked if it is: 1  A gasoline-powered vehicle with a 1991 model year and newer. 2  A light-duty truck at least 8,500 lbs. or heavier.