1. 1 Zinc Data EPP 245 Statistical Analysis of Laboratory Data

2. October 25, 2007EPP 245 Statistical Analysis of Laboratory Data 2. insheet using "Zinc.raw" (2 vars, 91 obs). do "zinc.do". regress peakarea concentration Source | SS df MS Number of obs = 91 -------------+------------------------------ F( 1, 89) =55116.45 Model | 2.6694e+11 1 2.6694e+11 Prob > F = 0.0000 Residual | 431037404 89 4843116.9 R-squared = 0.9984 -------------+------------------------------ Adj R-squared = 0.9984 Total | 2.6737e+11 90 2.9707e+09 Root MSE = 2200.7 ------------------------------------------------------------------------------ peakarea | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- concentrat~n | 7.207967.0307024 234.77 0.000 7.146962 7.268972 _cons | 104.5429 267.137 0.39 0.696 -426.2527 635.3385 ------------------------------------------------------------------------------. scatter peakarea concentration || lfit peakarea concentration. graph export zinc1.wmf, replace. rvfplot. graph export zinc2.wmf, replace. display (1850-_b[_cons])/_b[concentration] 242.15664

3. October 25, 2007EPP 245 Statistical Analysis of Laboratory Data 3

4. October 25, 2007EPP 245 Statistical Analysis of Laboratory Data 4

5. October 25, 2007EPP 245 Statistical Analysis of Laboratory Data 5. keep if concentration == 0 (83 observations deleted). list concentration peakarea +---------------------+ | concen~n peakarea | |---------------------| 1. | 0 115 | 2. | 0 631 | 3. | 0 508 | 4. | 0 317 | 5. | 0 220 | |---------------------| 6. | 0 93 | 7. | 0 99 | 8. | 0 135 | +---------------------+. summarize peakarea Variable | Obs Mean Std. Dev. Min Max -------------+-------------------------------------------------------- peakarea | 8 264.75 205.0343 93 631. display 264.75 + 3*205.03 879.84.