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.
Subtract breakeven sales from actual or budgeted sales to arrive at the margin of safety. Divide the margin of safety by actual or budgeted sales and multiply the resulting figure by 100 to get the margin of safety ratio in percentage. Following the above example, a budgeted sales amount of $850,000 would give a $100,000 margin of safety or 11.76 percent.