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.
The Calculation. To calculate profit margin at the product level, start with the selling price of the item -- what you charge customers for it. Now subtract the cost of the product to you -- how much it cost you to obtain it or produce it.The resulting figure is your gross profit on the item.he Calculation. To calculate profit margin at the product level, start with the selling price of the item -- what you charge customers for it. Now subtract the cost of the product to you -- how much it cost you to obtain it or produce it.