Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2022/ib/paper-3/18h/d/solution

Let . Under , the two residual sums of squares are independent and satisfy
Hence
Under , the numerator is scaled by the smaller variance, so small values provide evidence against the null. If denotes the lower quantile, a size- test rejects when

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