Final Exam #11: Sleep specialists want to study whether the supplement skullcap helps patients sleep better. What type of study should be conducted if the researches want to be able to establish whether or not that taking skullcap causes an improvement in the quality of sleep? O All of these choices will work to establish a causal relationship. O Randomly assign patients who volunteered for the study to one of two groups: either a group that takes skullcap or a group that takes a placebo, then compare the quality of sleep for the patients. O Collect a random sample of patients and ask them to answer a survey that asks them whether or not they took skullcap the night before and to rate the quality of their sleep on a scale of 1 to 5. O Identify patiends by their typical hours of sleep, divide them into groups based on gender and compare quality of sleep for the male and female participants