请问可以解释一下这里df1 和df2怎么判断么

问题如下：

Pres party dummy is equal to 1 if the US President is a member of the Democratic Party and 0 if a member of the Republican Party.

Is the regression model as a whole significant at the 0.05 level?

选项：

A.

No, because the calculated F-statistic is less than the critical value for F.

B.

Yes, because the calculated F-statistic is greater than the critical value for F.

C.

Yes, because the calculated χ2 statistic is greater than the critical value for χ2.

解释：

The F-test is used to determine if the regression model as a whole is significant.

F = Mean square regression (MSR) ÷ Mean squared error (MSE)

MSE = SSE/[n – (k + 1)] = 19,048 ÷ 427 = 44.60

MSR = SSR/k = 1071 ÷ 3 = 357

F = 357 ÷ 44.60 = 8.004

The critical value for degrees of freedom of 3 and 427 with (one-tail) is F = 2.63. The calculated F is greater than the critical value, and you should reject the null hypothesis that all regression coefficients are equal to zero.