7 . The R² measures:

A. The amount of variation there is in the data

B. How much the regression is able to explain variation in the dependent variable

C. How much we can claim causality for the estimated effect

D. The unexplained variation

12. Consider that 2 statistical agencies each collect independently data about wages and education levels. Each agency draws its own random sample of the UK population. The following is true:

A. If we estimate a simple regression model with wage as dependent variable and education as explanatory variable, then the parameter estimates using one sample will be the same of the parameter estimates using the other sample

B. If the first sample has less observations than the second, then the first sample is always preferable

C. One of the two samples cannot be used for any analysis

D. If we assume that the random variable wage in the population is distributed as a normal random variable with mean M and variance V, then we expect that the average of wage in both samples is close to M