The Rolling Stones, a rock group formed in the 1960s, have toured extensively in support of new albums. Pollstar has collected data on the earnings from the Stones's North American tours. For 30 randomly selected Rolling Stones concerts, the mean gross earnings is $2.27 million. Assuming a population standard deviation gross earnings of $0.5 million, obtain a 99% confidence interval for the mean gross earnings of all Rolling Stones concerts. Interpret your answer in words.