Check the applicability of Chebyshev's theorem and the empirical rule for the data set in given problem.
Problem
The following data are annualized returns on a group of 15 stocks.
12.5, 13, 14.8, 11, 16.7, 9, 8.3, -1.2, 3.9, 15.5, 16.2, 18, 11.6, 10, 9.5
Find the median, the first and third quartiles, and the 55th and 85th percentiles for these data.