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.
HomeDrugTestingKit.com reports that benzodiazepines, sedatives including such drugs as Ativan and Xanax, can remain in the system for up to 10 days. The opioid family of medication, including such drugs as Percocet and Vicodin, can also last up to 10 days in the body. Anti-depressants also last up to 10 days in the body, especially if you have been taking them regularly for longer than a month.