$\hat { \beta } - \beta$ A) Cannot Be Calculated Since the Population Parameter Is Unknown

Multiple Choice

$\hat { \beta } - \beta$

A) cannot be calculated since the population parameter is unknown.
B) $= \left( \boldsymbol { X } ^ { \prime } \boldsymbol { X } \right) ^ { - 1 } \boldsymbol { X } ^ { \prime } \boldsymbol { U }$
C) $= \boldsymbol { Y } - \hat { Y }$
D) $= \boldsymbol { \beta } + \left( \boldsymbol { X } ^ { \prime } \boldsymbol { X } \right) ^ { - 1 } \boldsymbol { X } ^ { \prime } \boldsymbol { U }$