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.
According to the Securities and Exchange Commission, operating margin is generally expressed as a percentage. To calculate the operating margin, you need to know the company's operating income and net sales. Step 1. Total the amount of business operating income during the specified period. Operating income equals the company's total profit before taxes and interest payments are factored into the mix.