The age when smokers first start from previous studies is normally distributed with a mean of 13 years old with a population standard deviation of 2 1 years old A survey of smokers of this generation was done to estimate if the mean age has changed The sample of 30 smokers found that their mean starting age was 12 5 years old Find the 90 confidence interval of the mean Do not round in between steps Round answers to at least 3 decimal places Give your answers as decimals to two places