26	26	25	17	16	16	14	17	21	16
16	18	17	15	15	19	16	17	22	15
19	17	16	27	16

The smallest number is 14 and the largest is 27.

Count the 14's.  There is only 1.  So the frequency of 14 is 1. 
Count the 15's.  There are 3.  So the frequency of 15 is 3.
Count the 16's.  There are 7.  So the frequency of 16 is 7.
Count the 17's.  There are 5.  So the frequency of 17 is 5.
Count the 18's.  There is only 1.  So the frequency of 18 is 1.
Count the 19's.  There are 2.  So the frequency of 19 is 2.
Count the 20's.  There aren't any.  So the frequency of 20 is 0.
Count the 21's.  There is only 1.  So the frequency of 21 is 1.
Count the 22's.  There is only 1.  So the frequency of 22 is 1.
Count the 23's.  There aren't any.  So the frequency of 23 is 0.
Count the 24's.  There aren't any.  So the frequency of 24 is 0.
Count the 25's.  There is only 1.  So the frequency of 25 is 1.
Count the 26's.  There are 2.  So the frequency of 26 is 2.
Count the 27's.  There is only 1.  So the frequency of 27 is 1.

So all you do is list the values under a column labeled X,
and their frequencies in a column beside it labeled f:

X    f
14   1
15   3
16   7
17   5
18   1
19   2
20   0
21   1
22   1
23   0
24   0
25   1
26   2
27   1
  ----
    25

Notice that I added up the second column, the column
of frequencies to make sure I had counted all 25 numbers 
in the given data.

Here is the histogram:



Edwin