1. Lesson #8: Table of Random Digits

2. Questions... How many treatments are included in your experiment?
Can you divide that number into 10 equally? Can you divide that number into 100 equally? If you can’t do either, you may need to exclude one or more numbers.

3. ... and Answers
For 3 Treatments 0-2, 3-5, 6-8 (no 9) 1-3, 4-6, 7-9 (no 0) 00-32, 33-65, 66-98, (no 99) 01-33, 34-66, (no 00) For 4 Treatments 0-1, 2-3, 4-5, 6-7 (no 8,9) 00-24, 25-49, 50-74, 75-99
For 2 Treatments
0-4, 5-9
00-49, 50-99
For 5 Treatments
0-1, 2-3, 4-5, 6-7, 8-9
00-19, 20-39, 40-59, 60-79, 80-99

4. Remember…
When you assign numbers to the treatments, all digits must be used equally.
Bad: 0-3, 4-6, 7-9 (1st group has more numbers than rest)
Good: 1-3, 4-6, 7-9, 0 is excluded
Bad: 0-1, 2-4, 5-7, 8-9 (2 groups are size 2, 2 groups are size 3)
Good: 0-1, 2-3, 4-5, 6-7 (8, 9 excluded)
Good: 00-24, 25-49, 50-74, 75-99

5. On the Table of Random Digits…
There are 40 digits for each line.
If you are using 1 digit to identify which treatment a subject goes to (0-9), you can identify 40 subject’s assignments.
If you are using 2 digits to identify which treatment a subject goes to (00-99), you can identify 20 subject’s assignments.
If you reach a number which was excluded, just skip it and go onto the next one.

6. Continued… You keep going until you have the right number of subjects
For example, if you want 50 subjects and you are using the numbers 0-9, you use 0-4 as Treatment 1 and 5-9 as Treatment 2.
Choose a line, count out 50 numbers, keeping track of how many 0’s, 1’s, 2’s, 3’s, and 4’s there are…these will get Treatment 1; the rest will get Treatment 2.
If you did this several times, with different lines, you should get similar results.
What if you did this with odd/even? Would you get similar results? Why or why not?

7. GW #12: Trick or Treatment
Use the Table of Random Digits:
Draw 2, 3, 4, and 5 treatment randomized comparative experiment diagrams.
For each one, name the treatments. You can call the treatments “Treatment #1”, “Treatment #2”, … or give them actual names if you wish.
Assign 30 subjects for each diagram, using the table (you may need to start a number on one line and finish it on the next line—that’s ok).
After done, write your results on the board (hopefully everyone didn’t use line 101) so we can see if the results are similar.