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.
There are two major ways to represent the results of a total margin ratio equation. The first is as a ratio that compares revenue to expenses. Using a ratio, the benchmark for breaking even is 1:1, or 1.0. The other way to express total margin ratio is as a percentage. Here the benchmark becomes zero. Total margin ratio percentages can be positive to indicate profit, or negative to indicate a loss.