1 Onset of sleep from time the lights were turned off; this is called  sleep onset latency  and normally is less than 20 minutes. ( 2 Note that determining sleep and awake is based solely on the EEG. Patients sometimes feel they were awake when the EEG shows they were sleeping.
The direct cost margin is calculated by taking the difference between the revenue generated by the sale of goods or services and the sum of all direct costs associated with the production of those goods, divided by the total revenue.
Divide your gross profit by your total revenue generated. In this example, you would divide $1,800 by $11,800 to get 0.15. Multiply the result from Step 2 by 100 to find the gross profit margin percentage. Finishing the example, you would multiply 0.15 by 100 to find that your gross profit margin equals 15 percent.