A researcher wonders how well the sense of smell functions during sleep. In general, we know that our sensory systems operate at a higher threshold during sleep. That is, a more intense stimulus is required to elicit a response during sleep than during wakefulness. Furthermore, we are less responsive during some stages of sleep than during others. Experiments using sounds suggest that we are less responsive during stages 3 and 4 sleep (deep sleep) than during stages 1, 2, or REM sleep (lighter sleep). Thus, the 4 – 16 researcher predicts that research participants will be less responsive to odors during stages 3 and 4 sleep than during the other stages of sleep. The researcher devises a system for delivering odors while college students sleep in the laboratory. Peppermint fragrance is delivered at specific times through a modified oxygen mask that the students wear while they sleep. Electrodes are attached to each students scalp, face, and chin to determine sleep staging. Electrodes are also attached to each students chest to record heart rate. A change in heart rate following presentation of the odor is used to indicate that the participant detected the odor.

Read the scenario above and answer the following questions:

What is the research hypothesis?
What is the independent variable?
Is the independent variable a qualitative variable or a quantitative variable?  Explain. 
Why might the researchers want to use multiple dependent variables?
Describe one limitation of this study. 

answer in 250-300 words 
use at least 1 reference