The data set

2, 3, 5, 6, 6, 8

   x   x-m  (x-m)²
   2   -3     9
   3   -2     4
   5    0     0
   6    1     1
   6    1     1
   8    3     9
6)30       6)24
   5          4

so m = 5, and s = 4

There are many possibilities.

Some other answers are listed below
 

data set: 1, 4, 6, 6, 6, 7

data set: 1, 5, 5, 5, 7, 7

data set: 2, 3, 5, 6, 6, 8 (the one above)

data set: 2, 4, 4, 5, 7, 8

data set: 3, 3, 3, 7, 7, 7

data set: 3, 3, 5, 5, 5, 9

data set: 3, 4, 4, 4, 6, 9

Edwin