Featured post

A walk in the Park

This blog is dedicated to everyone who has struggled with Community Medicine. Through my posts I hope to simplify and demystify community medicine. The emphasis will be on clarifying concepts rather than providing ready-made answers to exam questions.

Feedback is crucial for the success of this endeavour, so you are encouraged to comment and criticize if you cannot understand something.

If you want a topic to be discussed sooner rather than later, please let me know via

Facebook: http://www.facebook.com/pages/Community-Medicine-for-ALL/429533760433198  

[Alternatively, you may join the group communitymedicine4ALL: 


Twitter: @DocRoopesh

A single example may not be able to explain 100% of a given topic, so multiple examples may be provided to explain different parts of a single concept.

If something doesn’t seem right:

a. Write to me about it (at commed4all@gmail.com), and

b. Cross check with another source (textbook, expert, etc.)

I hope that my exertions will make your experience with community medicine seem like a “Walk in the Park”

Note 1. Those who wish to contact me on facebook are requested to kindly send a personal message introducing themselves along with the request. This will help save time and effort of all concerned. Please do not expect me to visit your page to try and identify you/ your areas of work/ interest, etc. It is common courtesy to introduce oneself to another when interacting for the first time. I am merely requesting that the same civil courtesy be extended here, too. Henceforth, I may not accept any friend requests/ requests to join the group on facebook unless accompanied by a note of introduction (except when I already know the sender).  

Note 2. Please understand that this blog (and the corresponding facebook page/ group) is maintained in my spare time. I have a full time job, and am available to pursue these activities only after regular working hours (after 5 pm Indian Standard Time). However urgently you may wish to receive a response from me, I will be able to respond only upon returning home from work (I am offline the rest of the time).

Note 3. Please mind your language when interacting with me/ in the group linked to this blog. Rude/ offensive language will result in expulsion from both my friends list and the said group.

Enhanced by Zemanta

Null Hypothesis Significance Testing: What you should know (Part 3)

In previous articles we have considered some basic concepts related to null hypothesis significance testing. This article will discuss the origins of null hypothesis significance testing.

The origins of Null Hypothesis Significance Testing

Although the popular perception is that significance testing is a modern concept, its origins can be traced back to the 18th century. Further, the modern approach of Null Hypothesis Significance Testing (NHST) is a combination of two distinct approaches: Fisher’s significance testing, and Neyman-Pearson’s hypothesis testing. We will consider these briefly in turn.

First significance test?

John Arbuthnot (physician to England’s Queen Anne) is credited with performing the first significance test. He examined birth records in London for the years 1629-1710 and observed that the number of male births exceeded female births every year. Assuming excess male births as likely as excess female births (the null hypothesis in modern terms), he calculated the probability of the observed outcome to be 0.5^82 (or 2.067952 *10^-25). He concluded that this very small probability ruled out chance and provided evidence for the existence of God.

In modern terms, he rejected the null hypothesis at p = ½^82 significance level. Of course, Arbuthnot did not use any of the terms used in modern null hypothesis significance testing to describe his observations.