E-drug: sampling drugstores (cont)
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Dear Arturo,
These steps are recommended in the INRUD/WHO PRDU Course material for
studying drug use problems, using a systematic random sampling
technique:
1. Define your sampling frame, this is the list of all drug stores in the
city which met your study criteria (A).
2. Define your sampling size (B), 20 is recommended.
3. Calculate the sampling interval (A divided by B = C).
4. Use a random number table with 3 decimals, which contains values
from 0.000 to 0.999. You may find the table in any statistics book.
Choose any number randomly, e.g. by using your finger tip while
closing your eyes (e.g. 0.563).
5. Multiply C by 0.563 (=D), round it up (=E). This value indicates the
order of drug store on your sampling frame (or list) you have to pick as
the first sample.
6. Add D to E. Round it up if necessary. This value indicates the order of
drug store you have to pick from your sampling frame, as the second sample.
7. Go on the same procedure as step 6, until you get the number of drug
stores you need (the sampling size).
Best regards,
Surya
Dr. Sri Suryawati
Pharmacist
Head of Clinical
Pharmacology Department, Faculty of Medicine, Gadjah Mada University.
Coordinator of INRUD-Indonesia
Sri Suryawati <suryawati@yogya.wasantara.net.id>
[Address details added by co-moderator. BS]
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