Title: Collecting a simple random sample - Listed as a step by step process - Return here if you have questions about the process along the way.
Course: Introduction to Statistics

As stated in the earlier presentation, collecting a simple random sample (SRS) is similar to drawing names out of a hat.  Everyone has the same likelihood of being chosen.  It is actually a simple process:

1.  List all subjects that are available

2.  Assign each subject a number.  I like to start with 1 and count up.  It is possible to start with 0.  Whatever the length of the number assigned to the last subject, every other number needs to have the same length.  For instance if the last subject is 437, then all numbers need to be 3 digits long.  Therefore the new numbering system will be 001, 002, 003, ...., 437.

3.  Now we will use the table of random digits (listed under resources) to randomly chose a number of subjects.  You can start anywhere you wish to on the list.  It is numbered so that if multiple students start at the same place, they are able to compare their selections.  Pull up the list of random digits.  We will start at line 132.  We look at 3 digit numbers to select our subjects.  The first string of digits is 68732.  We look at the first 3 (687) and since we don't have any subjects with this number, we disregard it.  We then take the next 3 digits, moving into the next string.  We now have 325, which is one of our subjects.  This was the first one drawn out of the hat.  We continue doing this until we have all the subjects that we need.  When we get to the end of a row there are a couple of options.  Since there are 40 digits in the row and we are looking for groups of 3, the last digit will still be there after 13 three digit numbers have been chosen.  We can either use the last digit and go into the next row for the following two digits or just disregard the remaining digit and start with a new row.  Either method is appropriate as long as you tell the reader what you are doing.