Stats and mean / sd

Question

Jennifer's scores in A2 this year are 100,85,55,95,75,68,78,88,94,91, and 77. Find the mean and standard deviation. What percent of these scores are within one standard deviation of the mean? Round all statistics to the nearest tenth. 

Answer 1

Mean =100+85+55+95+75+68+78+88+94+91+ 77/11=906/11=82.36

 

Variance = s²=Σ(xi−mean)²/n−1

Standard deviation =√s²

Count (n): 11
Mean: 82.36
Sum of Squares: 1777

Variance: 177.7

Standard Deviation: 13.33
68% of a normal distribution's values are within one standard deviation of the mean

Mean ±σ =82.36±13.33   

                    (69.03,    95.69)