what is the expected value of the fourth term what is the expected value of the third term of $sigma what type of model is hat-sigma? how to use the standard regression assumptions to prove that $hatsigma2$ is an unbiased estimator of $sigma2$? what should the expected value of the third term be? how do you find an unbiased estimator of a term what is the expected value of a term in an equation? which statement should be used for the standard regression assumption that $hatsigma2 is an unbiased estimator of $sigma2$? how to use standard regression assumptions how do you find out the standard regression value for 2$ if the expected value of the third term is $2, how to use it is hat sigma unbiased what does hat-sigma mean what is the expected value of the second term how to prove that hat sigma is unbiased what term is $sigma when comparing the standard regression assumptions with the expected value of the first term, how do you get the expected value? how to use standard regression what is the expected value of a tenth term how to use the standard regression assumption to prove that $hat sigma2 is an unbiased estimator