. regress elevation i.wgrp Source | SS df MS Number of obs = 75 -------------+---------------------------------- F(2, 72) = 1.03 Model | 4434.12986 2 2217.06493 Prob > F = 0.3617 Residual | 154765.95 72 2149.52708 R-squared = 0.0279 -------------+---------------------------------- Adj R-squared = 0.0008 Total | 159200.08 74 2151.35243 Root MSE = 46.363 ------------------------------------------------------------------------------ elevation | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- wgrp | 2 | 18.82543 13.11343 1.44 0.155 -7.31572 44.96659 3 | 8.912666 13.11343 0.68 0.499 -17.22849 35.05382 | _cons | 1181.577 9.272599 127.43 0.000 1163.093 1200.062 ------------------------------------------------------------------------------ . regress elevation 3.wgrp Source | SS df MS Number of obs = 75 -------------+---------------------------------- F(1, 73) = 0.00 Model | 4.1675212 1 4.1675212 Prob > F = 0.9653 Residual | 159195.912 73 2180.76592 R-squared = 0.0000 -------------+---------------------------------- Adj R-squared = -0.0137 Total | 159200.08 74 2151.35243 Root MSE = 46.699 ------------------------------------------------------------------------------ elevation | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- 3.wgrp | -.5000513 11.43879 -0.04 0.965 -23.29753 22.29743 _cons | 1190.99 6.604189 180.34 0.000 1177.828 1204.152 ------------------------------------------------------------------------------