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.
Not Worth the Risk. How long marijuana stays in your system depends on your body and health, the amount of daily use and how long you have been smoking. Heavy users will find that pot can be detected in their system for weeks, while lighter users will have it run through in a week.