Mean: average value in a population. Standard Deviation: measure of dispersion (i.e. how spread out are your numbers?)
Total cannabinoid (TC) content (the sum of all cannabinoids by weight) is normally distributed within varieties. By definition under this distribution pattern, 95% of observations within a specific variety will fall within 2 standard deviations of the mean.
Let's assume a variety has a mean TC of 15% and a standard deviation of 2%. 68% of the population will have a TC ranging between 13%-17%, 95% will fall between 11% and 19%, and 99.7% will be between 9%-21%. Assuming a 27:1 CBD to THC ratio, a farmer could expect random sampling of finished flowers to contain anywhere between 0.34% and 0.8% total THC with an average of 0.57%. This is obviously a tremendous amount of variation.
Why should anyone care?
The newest way that hemp seed makers are misleading farmers is directly related to this underlying statistical reality. Many are posting a single COA for their variety--8% CBD and 0.29% THC for example--and claim that they have developed a federally compliant cultivar. The problem? A single plant is not representative of the population--and federal compliance requires that 95% of the population be compliant due to the sampling techniques required by the USDA and state departments of agriculture. If the mean TC were 8% and the standard deviation 2%, 95% of the population would fall between 4% and 12% TC, with total THC values ranging from 0.15% to 0.46%.
Inbreeding can reduce the magnitude of standard deviations; however, population data across hundreds of cultivars and many thousands of tests (our own and aggregated from all known cannabis science literature) suggests that the average standard deviation within any randomly selected cannabis population is 1.96%. Given that reality, to attain a federally legal crop 95% of the time (i.e. maximum TC = 8%), the mean TC for a pure type III variety must be approximately 4%.
The moral of the story? No one is able to honestly offer 95% compliant CBD varieties that are economically competitive.
Creating 100% federally legal CBD varieties requires a different approach.