Testing Accuracy and Precision: Durban Poison
At PREE, we’re always looking for ways to stress-test our processes and validate our ability to deliver accurate and precise results (more on the distinction between the two below). So our team decided to stop by a local dispensary to pick up some flower and bring it back to the lab.
We selected some Durban Poison, a prevalent strain here in Oregon. It averages a THC concentration around 20%, and the product label indicated that the testing lab for this batch produced a potency result of 22.46%.
When we test a sample, we’re looking for two key indicators of reliability — accuracy and precision. Accuracy refers to how close the measurement is to the true value, while precision refers to how close the measurements are to each other. It is possible to have just one or the other — or neither — and we of course expect to see both for every sample that comes through our lab.
We ran the Durban Poison flower three times and produced results ranging from 21.82% to 22.11% for an average of 22.01% — an accurate match for the potency on the label. And the relative standard deviation (%RSD) or relative percent difference (RPD) between the three results is just 0.76% — well below the OLCC’s variance tolerance of 10%. That’s precision.
Why is our average result lower than that on the label? As you can see, this product is from September, and cannabis slowly loses THC potency over time depending on storage conditions. So the measurable, albeit minor, difference in concentration is to be expected over a four-month period.
Everyone in the cannabis community — from producers to dispensaries and consumers — depend on accuracy and precision from testing labs. We take that responsibility seriously, and we also look to take the extra step beyond the metrics. We’ll happily rerun a sample, help make sense of the results, and discuss potential contributing factors that led to the outcomes. It’s not just about the number — it’s about the impact.
About Durban Poison (from Leafly) — This pure sativa originates from the South African port city of Durban. It has gained popularity worldwide for its sweet smell and energetic, uplifting effects. Durban Poison is the perfect strain to help you stay productive through a busy day, when exploring the outdoors, or to lend a spark of creativity. Growers and concentrate enthusiasts will both enjoy the over-sized resin glands which make this strain a quality choice for concentrate extraction. The buds are round and chunky, and leave a thick coating of trichomes on almost all areas of the plant.