Statistics-Recent blogs on our website had the below information

Recent blogs on our website had the below information. I don’t understand how if p = 2 the degrees of freedom could be n-3?

Hi,

Given a model which includes quadratic term y=b₀+b₁x+b₂x²+e, if we want to use t test to figure out the p-value of the parameters b₀, b₁, b₂, what is the degree of freedom of the t distribution? n-3?

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Message ReadMark as Unread Message Not FlaggedSet FlagDecember 6, 2015 8:24:28 PM PST1 day ago Lang Wu UBC InstructorManagerRE: degree of freedom in linear regressionCollapse

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Yes, n-3. The degree of freedom is n-p-1, where p is the number of predictors. Here p=2 since you may view x2=x²