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Technology Californians getting Smog Checks today may notice that the traditional tailpipe test used for many years has been replaced by a quicker, computer-based test for gasoline-powered cars model-year 2000 and newer, and for most diesel vehicles that are model-year 1998 and newer.
Why can't You Sell a Car in California with a Smog Certificate After 90 Days of Obtaining it? The state DMV provides guidelines for selling cars that are more than four model years old with a California smog certificate. The DMV states that the effective period for a smog certificate is 90 days. Beyond that, a smog certificate will not be effective for selling the car. The intention of this law is to provide for ensuring that cars sold to new owners have been recently inspected for emissions.