9.7 , 9.7 , 9.9 , 9.9 , 10.0 , 10.1 , 10.2 , 10.5
The mean and the standard deviation of the 8 numbers shown above is 10 and 0.25 respectively. What percent of the 8 numbers are within 1 standard deviation of the mean? Answers.
A) 90%	B) 85%	C) 80%	D) 75%	E) 70%
Within 1 standard deviation of the mean- means in the range {mean-1*sd; mean+1*sd} = {10-1*0.25; 10+0.25} = {9.75; 10.25}.   From the 8 listed numbers, 5 are within this range so 5/8=75%.   Answer: 75%.
<result>D</result>
9.7 , 9.7 , 9.9 , 9.9 , 10.0 , 10.1 , 10.2 , 10.5
The mean and the standard deviation of the 8 numbers shown above is 10 and 0.25 respectively. What percent of the 8 numbers are within 1 standard deviation of the mean?