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Technology Californians getting Smog Checks today may notice that the traditional tailpipe test used for many years has been replaced by a quicker, computer-based test for gasoline-powered cars model-year 2000 and newer, and for most diesel vehicles that are model-year 1998 and newer.
Checking for Dangerous Gases. One of the main reasons why vehicles are asked to undergo a smog check is to monitor 5 gases â hydrocarbons, carbon monoxide, nitrogen oxides, carbon dioxide, and oxygen. More often than not, the end result for a smog test to fail is high levels of these gases.