The T-Score Formula. The t-score is a fraction. The numerator is the sample's mean minus mean of the group you are comparing the sample to, and the denominator is the sample's standard deviation divided by the square root of the sample size.
If you have smoked marijuana then the drug will stay for 3 to 30 days. This is normal for the common drugs. But in the case of marijuana, this can be detected even after a month in Urine drug test marijuana. Marijuana will stay in your system for 10 days if you have been smoking occasionally.
I have found that it varies by person and by substance. generally, weed stays in your fat cells (and therefore urine) for anywhere from 3 weeks - 3 months. although your first time it goes away a lot faster (like 3-7 days). opiate pain pills and some other prescription narcotics last in your system for 4-6 hours and the metabolized chemical precursors (which are what actually show up on drug tests)are gone after 2-5 days. with the exception of DXM, OTC drugs don't show up at all on tests ...