15.65 Three real estate agents were each asked to assess the values of five houses in a neighborhood. The results, in thousands of dollars, are given in the table. Prepare the analysis of variance table, and test the null hypothesis that population mean valuations are the same for the three real estate agents.

Agent House A B C 1 210 218 226 2 192 190 198 3 183 187 185 4 227 223 237 5 242 240 237