2. the ols estimators of the coefficients in multiple regression will have omitted variable bias a) if and only if the omitted variable is not mean zero. b) if and only if the omitted variable has a positive coefficient. c) always. d) if and only if the omitted variable is a determinant of y and is correlated with at least one of the regressors.

The two-way table shows the number of people whose hobbies are reading or solving puzzles and who either ride a motorcycle or don’t ride a motorcycle. among people whose hobby is reading, what is the relative frequency of not riding a motorcycle? express your answer as a decimal, and round it to the nearest hundredth if necessary. enter your answer in the box. reading solving puzzles ride a motorcycle 7 3 don't ride a motorcycle 5 9

Hi, can anyone show me how to do this problem? 100 points for this. in advance

Two airplanes start at the same place and travel in opposite directions,one at 395 miles per hour and the other at 422 miles per hour. how many hours will it take for the planes to be 2451 miles apart?