$($Definitions and concepts$)$ Define or describe the followings. Stick to the nota$-$

tion from the lectures. You need to add your explanations in words, if you use

mathematical expressions. Be complete and concise. Adding irrelevant material

will be penalized.

$($a$)$ Endogeneity

$($b$)$ Significance level

$($c$)$ P$-$value

$($d$)$ Perfect collinearity

$($e$)$ Multicollinearity

$($f$)$ The multicolinearity problem

$($g$)$ The bias$-$variance tradeoff in adding an additional independent variable

$($specify the conditions of the tradeoff$)$

$($h$)$ Dummy variable trap