18. Archaeology: Ireland The Hill of Tara in Ireland is a place of great ar- chaeological importance. This region has been occupied by people for more than 4000 years. Geomagnetic surveys detect subsurface anomalies in the earth's magnetic field. These surveys have led to many significant archaeological discoveries. After collecting data, the next step is to begin a statistical study. The following data measure magnetic susceptibility (centimeter-gram-second X 10 ) on two of the main grids of the Hill of Tara (Reference: Tara: An Archaeological Survey by Conor Newman, Royal Irish Academy, Dublin). Grid E: x variable 13.20 5.60 19.80 15.05 21.40 17.25 27.45 16.95 23.90 32.40 40.75 5.10 17.75 28.35 Grid H: y variable 11.85 15.25 21.30 17.30 27.50 10.35 14.90 48.70 25.40 25.95 57.60 34.35 38.80 41.00 31.25 (a) Compute Ex, Ex?, Zy, and Ey. (b) Use the results of part (a) to compute the sample mean, variance, and standard deviation for x and for y