Answer:
The sample mean year is 1261 A.D.
The standard standard deviation is of 46 A.D.
Explanation:
Sample mean:
Sum of all values divided by the number of values. So
Rounding to the nearest whole number, the sample mean year is 1261 A.D.
Sample standard deviation:
Square root of the sum of the difference squared between each value and the mean, divided by one less than the sample size. So
Rounding to the nearest whole number, the standard standard deviation year is of 46 A.D.