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 equation for calculating the monetary value of gross margin is: gross margin = sales â cost of goods sold A simple way to keep markup and gross margin factors straight is to remember that: Percent of markup is 100 times the price difference divided by the cost. Percent of gross margin is 100 times the price difference divided by the selling price. Gross margin (as a percentage of Revenue)