Final answer:
A method used to study sleep that can provide qualitative data is through interviews or open-ended surveys. By asking participants about their experiences, thoughts, and feelings during different stages of sleep, researchers can gather qualitative data that provides insights into the subjective aspects of sleep.
Step-by-step explanation:
A method used to study sleep that can provide qualitative data is through interviews or open-ended surveys. By asking participants about their experiences, thoughts, and feelings during different stages of sleep, researchers can gather qualitative data that provides insights into the subjective aspects of sleep. For example, participants may describe their dreams or how they feel upon waking up. This type of data cannot be easily quantified or represented numerically, but it can provide rich information about the individual experiences of sleep.