At Burnt Mesa Pueblo, archaeological studies have used themethod of tree-ring dating in an effort to determine whenprehistoric people lived in the pueblo. Wood from severalexcavations gave a mean of (year) 1239 with a standard deviation of43 years. The distribution of dates was more or less mound-shapedand symmetrical about the mean. Use the empirical rule to estimatethe following.
(a) a range of years centered about the mean in which about 68%of the data (tree-ring dates) will be found
between  and  A.D.
(b) a range of years centered about the mean in which about 95% ofthe data (tree-ring dates) will be found
between  and  A.D.
(c) a range of years centered about the mean in which almost allthe data (tree-ring dates) will be found
between  and  A.D.
