Biostatistics in research methodology

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1. Dear Members,

A less random but

nevertheless useful approach is to use a systematic sampling scheme. In

this method, a number is assigned to every record, and then every nth record is

selected from a list. For example, if we want to systematically select 50 of

your 300 patients with angina, the procedure would be as follows:

1.

Obtain a list of all

300 patients with angina (this is our sampling frame).

2.

As 300/50 = 6, we

will be taking every 6th patient.

3.

Choose a number

randomly between 1 and 6 as a starting point.

4.

Take every 6th

patient thereafter (e.g. if our starting point is 4, we will take patient

numbers 4, 10, 16, 22, 28, 34, etc.).

By doing this, we are using

the list rather than our own judgement to select the patients. Look at the list

carefully before start selecting. For example, choosing every tenth patient in

a list of married couples may well result in every selected person being male

or every selected person being female. Regards,Dr. Vijaya Chaudhari.JR-3,Dept. of Pharmacology,Government Medical College, Nagpur.