5. Suppose that you get the following regression result from a sample of 277 observations: = 4.57 +0.188x1 - 0.22x2 + 0.171x3 0.92x4 (0.25) (0.040) (0.21) (0.055) (0.33) R = 0.353 The numbers in the parentheses are the heteroskedasticity robust standard errors for the OLS estimates. 2 (a) Compute t statistics for the coefficients on x2 and x4 (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 x2 has a significant effect on y or not. How about x4? Explain. (c) Compute the 95% confidence intervals for the estimated coefficients on x2 and x4. (d) What is the risk if we do not use the heteroskedasticity robust standard errors?