The following observations are copper contents (%) for a sample of Bidri artifacts (a type of ancient Indian metal handicraft) at the Victoria and Albert Museum in London (“Enigmas of Bidri,” Surface Engr. 2005: 333–339): 2.4, 2.7, 5.3, and 10.1. What confidence levels are achievable for this sample size using the signed-rank interval? Select an appropriate confidence level and compute the interval.