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.
Calculating Profit Margin. To calculate your profit margin, divide your profit by the amount of your gross sales. For example, if your company sells $100,000 worth of product and has $70,000 worth of expenses, then your profit is $30,000 and your profit margin is 30 percent, or $30,000 divided by $100,000.