If the estimates of the coefficients of interest change ...

[Engineer]

If the estimates of the coefficients of interest change substantially across specifications,
 
  A) then this can be expected from sample variation.
  B) then you should change the scale of the variables to make the changes appear to be smaller.
  C) then this often provides evidence that the original specification had omitted variable bias.
  D) then choose the specification for which your coefficient of interest is most significant.

Question 2

Applying the analysis from the California test scores to another U.S. state is an example of looking for
 
  A) simultaneous causality bias.
  B) external validity.
  C) sample selection bias.
  D) internal validity.

[tanna.moeller]

Answer to Question 1

Answer: C

Answer to Question 2

Answer: B

[Engineer]

Excellent

[carojassy25]

Gracias!