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.
In business and finance there are many types of margin. It simply means the distance between one financial point and another financial point; usually the higher the margin, the better. The most common type of margin revolves around profit and is known as the 'margin of safety' or simply 'profit margin'. In a business you have direct and indirect costs.