Answer: The margin of error is 12.74.
Explanation:
Since we have given that
Standard deviation = 6.5
Mean = 255
Let 95% level of significance,
So, z value = 1.96
We need to find the "Margin of error":
So, it becomes :
Margin of error = Standard deviation × z-value
Margin of error =

Hence, the margin of error is 12.74.