70 point Acetic acid curve by GC/FID demonstrates heterogeneity of variance in analytical data

These data are from a calibration of Acetic acid on a GC/FID instrument with a headspace autosampler with 70 calibrated points (10 points were targeted for each level, but replicates were weighed individually resulting in 70 unique amount points measured in mg). One major outlier was added after the fact to illustrate how outliers can pull the calibration model. These data illustrate problems with analytical data from chromatography experiments that largely go unnoticed because there's not enough data collected to see them, namely non-normal error, heteroscedasticity, and outliers.

There are 8 columns in the dataset, called "Level", "Amount", "Response", "ISArea", "DMIAmt", "STDAmt", "ISAmt", "ISAmount".

"Level" contains integer values corresponding to the specific vial prepared, numbered 1:70, not in that order.

"Amount" contains the amount of Acetic acid, in mg, in each vial run on the instrument, which was injected into the vial from a stock standard solution with a weighed concentration of Acetic acid and DMI. These data are sorted by "Amount".

"Response" is the gas chromatograph's (GC's) resulting area counts for the Acetic acid peak on each run.

"ISArea" is the GC's resulting area counts for the Ethylbenzene peak on each run.

The "Amt" columns are the balance weights for the internal standard solution, the reagent (DMI), and the stock standard solution added to each vial, measured in mg. These are not the Amounts of the individual standards in a vial.

"ISAmount" is the Amount of Ethylbenzene in the vial in mg.