Y = a1 + a2*X1 + a3*X1^2 + a4*d1 + a5*d2 + a6*d1*X1 + a7*d2*X1
d1 d2 是Dummy variables

请问是这样理解吗？ 还是有其他思路。 多谢了！


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A linear model has the following characteristics:
*A dependent variable (y)
*One continuous variable (xl), including a quadratic term (x12)
*One categorical (d with 3 levels) predictor variable and an interaction term (d by x1)
How many parameters, including the intercept, are associated with this model?
Enter your numeric answer in the space below. Do not add leading or trailing spaces to your
answer.
Answer: 7