Under the Least Squares Assumptions (Zero Conditional Mean for the Error

Short Answer

Under the least squares assumptions (zero conditional mean for the error term, Xi and Yi being i.i.d., and Xi and ui having finite fourth moments), the OLS estimator
For the slope and intercept a. has an exact normal distribution for $n > 15$ .
b. is BLUE.
c. has a normal distribution even in small samples.
d. is unbiased.