Finding arithmetic mean, standard deviation, mode and median On the market quality of the fruit was measured and following results came out:
Quality of Fruit( in measuring units ) 65 70 75 80 85 90 95 100  
Number                                  2  3  2  5  8 7  5  3 

Define:
   a) arithmetic mean and standard deviation
   b) mode and median
How to find what is wanted here?

Hint.  
Mean is the average, i.e. if I have $n$ numbers, $a_1, a_2,\dots, a_n$, their mean is
$$\mu=\frac{a_1+a_2+\dots+a_n}{n}=\frac{\sum_{m=0}^n a_m}{n}$$
Standard deviation, $\sigma$, is given by
$$\sigma=\sqrt{\frac{\sum_{m=1}^n a^2_m}{n-1}-\frac{n}{n-1}\mu^2}$$
A mode is the number that most often appears in a set of data. For example, the mode of 
1 2 2 3 4 5 6

is $2$.
Lastly, a median is the middle number of the data when it is sorted (or mean of the two middle numbers, if there is an even number of elements).  The mode of the above numbers is $3$.
