How the study of (reportedly) contaminated oat products could be improved

One sample can be very misleading.

It would have been better to collect five samples of each product to be tested, samples with five different manufacture or "best used by" dates to get a sense of the variation. Each sample should be tested separately.

If budget is limited, pick one product from each manufacturer and deep-dive.

Normalize by the percentage of oats. Rolled oats, aka oat meal is 100% oats so one might expect it to be higher. A granola product might only be 30% oats. One might assume that a manufacturer that is high on the basis of % oats will be high in other products because the content is likely to be from the same purchasing stream.

Include at least three organic products from different manufacturers in the universe that is tested. The author makes the assumption that "organic" products will not have any contamination. Good research goes to great efforts to wash-out bias and preconceptions. It goes to even greater effort to avoid perpetuating preconceptions that are not tested. The author does none of that.

Include some European products in the testing. The EU already has standards for that pesticide. If the EU products crash-and-burn in the California testing, the Ca testing is probably in error and might be "seeing" similar chemicals and adding their weight in the tally.

Another potential error is that active ingredients are often combined with an amide or chelating agent or a non-ionic "salt" to increase bioactivity, wettability or cuticle penetration. Great care must be taken to ensure the analytical report "backs out" the mass of the helper-chemistry and only reports the active ingredient.