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.
To calculate the contribution margin ratio, divide the contribution margin by sales. The contribution margin is calculated by subtracting all variable costs from sales.versonâs contribution margin ratio is 60%, so if it wants to break even, it needs to either reduce its fixed expenses by $60,000 or increase its sales by $100,000 (calculated as $60,000 loss divided by 60% contribution margin ratio).