The sample correlation coefficient is an estimator of the population correlation coefficient and measures the causal effect of one random variable on the other one. the covariance between two random variables. O how well their scatterplot is approximated by a straight line. the causal relationship between the two random variables. Question 56 The Gauss-Markov theorem is a proposition that establishes the assumptions under which OLS estimation generates the best linear unbiased estimators of the sample coefficients of a linear regression model. True False