Make a table with six rows and four columns. In row one, put the column headings. Column 1 is Number. Column 2 is Mean of All Numbers in Set. Column 3 is Number - Mean of All Numbers in Set. Column 4 is (Number - Mean of All Numbers in Set) Squared.
Start filling in the table. The numbers used here are examples. Any numbers will work. In column 1, put the numbers 6, 4, 7, 8, 0.
In Column 2, write the mean or average of 6, 4, 7, 8, and 0 in every blank. 6 plus 4 plus 7 plus 8 plus 0 divided by 5 equals 5, so write 5 in each blank.
In column 3, compute Number minus Mean, meaning column 1 minus column 2. Going down, you should have 1, -1, 2, 3, -5.
In column 4, compute (Number - Mean) squared. Going down, you should have 1, 1, 4, 9, 25.
Add the numbers obtained in Column 4. The result is 40.
Divide your answer in step 6 by 5, the number of entries. The result is 8.
Take the square root of your answer in step 7. You get 2.83 for your final answer.