Sheriff S. Norton Koch wants to know if the number of drug arrests in Weed County has increased since the 1990 passage of a tough new state law on drug possession. His dependent variable is the number of drug arrests. He has three independent variables: X₁ is a trend variable coded 1 in the first year and increasing by 1 each year thereafter; X₂ is a short-term impact variable coded 0 before 1990 and coded 1 afterward; and X₃ is a long-term impact variable coded 0 before 1990 (first year is 1980) and increasing by 1 each year afterward. A regression produces the following results:

Interpret the slopes and coefficient of determination. Test the slopes for significance, and explain what this equation says about the drug law.  

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Sb₁ = .92 $6₂ Ŷ 546.55.1X₁ = + 67.2X₂ + 4.3X3 34.1 = = 17.3 = 1.3 Sylx $6₂ R² = .99 N = 32