Question 1135886
To find the mean, add the numbers and divide the sum by the number of addends. 

The median is the middle number in a data set that is ordered from least to greatest. 

When there are two middle numbers, the median is the mean of these two numbers.

example:

{{{13}}}, {{{18}}}, {{{13}}}, {{{14}}}, {{{13}}}, {{{16}}}, {{{14}}}, {{{21}}}, {{{13}}}

The mean is the usual average, so I'll add and then divide:

{{{(13 + 18 + 13 + 14 + 13 + 16 + 14 + 21 + 13) / 9 = 15}}}

The median is the middle value, so first I'll have to rewrite the list in numerical order:

{{{13}}}, {{{13}}}, {{{13}}}, {{{13}}}, {{{14}}}, {{{14}}}, {{{16}}}, {{{18}}}, {{{21}}}

There are nine numbers in the list, so the middle one will be the {{{(9 + 1) / 2 = 10/ 2 = 5}}}th number:

{{{13}}}, {{{13}}}, {{{13}}}, {{{13}}}, |{{{highlight(14)}}}|, {{{14}}}, {{{16}}}, {{{18}}}, {{{21}}}

So the median is {{{14}}}.