Math Sheet Name Score Teacher Date Covariance of Random Variables State whether data are a population or sample. Use the specified denominator, keep paired observations together, and distinguish zero covariance from independence. 1. Let X be equally likely to be -11.3, 0, or 11.3, and define Y=X^2. Show Cov(X,Y)=0 and decide whether X and Y are independent. Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. 2. A joint PMF assigns probability 1/6 to each pair (63,128), (69,144), (69,148), (75,152), (75,156), (81,172). Find Cov(X,Y) using E(XY)-E(X)E(Y). Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. Show support, sums or integrals, and approximation assumptions. math-sheet.com Page 1 of 4
Math Sheet Name Score Teacher Date Covariance of Random Variables State whether data are a population or sample. Use the specified denominator, keep paired observations together, and distinguish zero covariance from independence. 3. Paired observations (7 pairs): (56,60), (60,66), (58,66), (62,66), (60,66), (64,72), (62,66). Treat these as a sample. Find covariance using denominator n-1. Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. 4. Paired observations (5 pairs): (-74,-222), (-70,-208), (-70,-206), (-66,-198), (-66,-196). Treat these as the whole population. Find covariance using denominator n. Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. Show support, sums or integrals, and approximation assumptions. math-sheet.com Page 2 of 4
Math Sheet Name Score Teacher Date Covariance of Random Variables State whether data are a population or sample. Use the specified denominator, keep paired observations together, and distinguish zero covariance from independence. 5. Paired observations (5 pairs): (70,215), (73,225), (74,229), (77,236), (78,240). Treat these as the whole population. Find Var(2X-Y). Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. 6. Paired observations (8 pairs): (49,197), (53,218), (53,223), (57,229), (57,234), (61,255), (61,245), (65,266). Treat these as the whole population. Find Cov(3X+2,3Y+4). Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. Show support, sums or integrals, and approximation assumptions. math-sheet.com Page 3 of 4
Math Sheet Name Score Teacher Date Covariance of Random Variables State whether data are a population or sample. Use the specified denominator, keep paired observations together, and distinguish zero covariance from independence. 7. Paired observations (5 pairs): (22,19), (27,27), (26,29), (31,28), (30,30). Treat these as the whole population. Find correlation. Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. 8. Paired observations (6 pairs): (-17,-52), (-13,-36), (-15,-38), (-11,-34), (-13,-36), (-9,-20). Treat these as the whole population. Find covariance using denominator n. Assumptions: The stated observations and denominator convention define the dataset; no pairs are omitted. Paired products use matching observations. Population covariance divides by n; sample covariance divides by n-1. Show support, sums or integrals, and approximation assumptions. math-sheet.com Page 4 of 4