A researcher is trying to determine whether a newly discovered substance X can be useful in promoting wound healing after surgery. She conducts this study by enrolling the next 100 patients that will be undergoing this surgery and separating them into 2 groups. She decides which patient will be in which group by using a random number generator. Subsequently, she prepares 1 set of syringes with the novel substance X and 1 set of syringes with a saline control. Both of these sets of syringes are unlabeled and the substances inside cannot be distinguished. She gives the surgeon performing the surgery 1 of the syringes and does not inform him nor the patient which syringe was used. After the study is complete, she analyzes all the data that was collected and performs statistical analysis. This study most likely provides which level of evidence for use of substance X?
ALevel 3
BLevel 1
CLevel 4
DLevel 5
ELevel 2
Which of the following study designs would be most appropriate to investigate the association between electronic cigarette use and the subsequent development of lung cancer?
ASubjects with lung cancer who smoke and subjects with lung cancer who did not smoke
BSubjects who smoke electronic cigarettes and subjects who smoke normal cigarettes
CSubjects with lung cancer who smoke and subjects without lung cancer who smoke
DSubjects with lung cancer and subjects without lung cancer
ESubjects who smoke electronic cigarettes and subjects who do not smoke
A resident in the department of obstetrics and gynecology is reading about a randomized clinical trial from the late 1990s that was conducted to compare breast cancer mortality risk, disease localization, and tumor size in women who were randomized to groups receiving either annual mammograms starting at age 40 or annual mammograms starting at age 50. One of the tables in the study compares the two experimental groups with regard to socioeconomic demographics (e.g., age, income), medical conditions at the time of recruitment, and family history of breast cancer. The purpose of this table is most likely to evaluate which of the following?
AObserver bias
BStatistical power
CConfounding
DRandomization
EEffect modification
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