Which formula correctly calculates the percentage of REM sleep (R) time?

Which formula correctly calculates the percentage of REM sleep (R) time?

• A. minutes of R / TST × 100
• B. minutes of R / TRT × 100
• C. minutes of R / TST
• D. minutes of R × TST

Answer: (A)

This is about expressing REM sleep as a percentage of total sleep time. To do this, take the minutes spent in REM, divide by the total sleep time in minutes, and multiply by 100 to convert the ratio to a percent. Using the total sleep time as the denominator reflects the portion of actual sleep that REM represents, not how long the recording lasted or some other time measure. If you divide by Total Recording Time, you’d be comparing REM to time that isn’t necessarily sleep, which isn’t the intended percent of sleep. Dropping the ×100 would give a decimal proportion rather than a percentage, and multiplying REM minutes by total sleep time doesn’t produce a meaningful percent.

This is about expressing REM sleep as a percentage of total sleep time. To do this, take the minutes spent in REM, divide by the total sleep time in minutes, and multiply by 100 to convert the ratio to a percent. Using the total sleep time as the denominator reflects the portion of actual sleep that REM represents, not how long the recording lasted or some other time measure. If you divide by Total Recording Time, you’d be comparing REM to time that isn’t necessarily sleep, which isn’t the intended percent of sleep. Dropping the ×100 would give a decimal proportion rather than a percentage, and multiplying REM minutes by total sleep time doesn’t produce a meaningful percent.