4. Suppose that you get the following regression result from a sample of 277 obsted! y = 4.57 +0.188 -0.222 +0.1713 - 0.924 (0.25) (0.040) (0.21) (0.055) (0.33) R = 0.353 er 1 The numbers in the parentheses are the heteroskedasticity robust standard errors for the OLS estimates. (a) Compute t statistics for the coefficients on 12 and 24 (The null hypothesis is that the coefficient is 0) (b) (1.96) = 0.975, where (.) is the CDF of a standard normal distribution. Given this information, explain whether 72 has a significant effect on y or not. How about r? Explain. c) Compute the 95% confidence intervals for the estimated coefficients on 12 and 14. (What is the risk if we do not use the heteroskedasticity robust standard errors? a a