Q1. A study produced the following data: x variable : 3900, 3220, 2790, 2770, 2160, 1810, 1770, 1680, 1500, 1270 y variable : 256.9, 238.1, 194.1, 187.3, 233.1, 124.7, 182.1, 31.9, 144.9, 126.9 (a) Compute Sxy and Sxx and estimate the regression coefficients a and b for the linear model Yi = a + bxi + i, where i i.i.d. N(0, ^2). (b) For the slope b of the regression line, test the hypothesis b = 0 at 95% confidence level. (c) Reduce now the number of data categories by dividing xi's into those that are low, that is, less or equal to the sample meanx, and those that are high, that is strictly larger than the sample mean. Do the analogous for yi's. Treating the modified data as a 2 2 contingency table, test whether having low or high y is independent of having low or high x at 95% confidence level.