Friday, June 24, 2011

Test for homogeneity of variance: Bartlett test

First an important assumption: that the normal distribution is followed by the data.
Null hypothesis for this test is that the variances are equal in the groups.
So if, p value less than 0.05, null hypothesis is rejected and interpretation being that the variances are not equal (or homodescacity is absent).

In case, the normality assumption is violated, then we can go for Levene test.

For further discussion using R:

Test for normality: Shapiro Wilk test

In order to test the normality of the distribution pattern of a variable, we can use the Shapiro Wilk test. The null hypothesis is that: There is no difference in the distribution of the given data and a normal distribution curve (or in other words the data is normally distributed).
So if the P value is less than 0.05, means that the null hypothesis is rejected or in other words, there is a difference in the distribution of the given data and a normal distribution curve or the given data is not normally distributed.

For this type of data which is not normally distributed, it is time to go for a non parametric test.

Note: Shapiro Wilk can be used to test the normality of residuals in a linear regression model. In R using the epicalc package, it can be done as: shapiro.test(lm(age ~ case.factor)$residuals). In this example, age is the numerical variable and case.factor is the categorical variable as cases and controls and lm stands for linear model.

Monday, June 13, 2011

My comments for the Medical Council of India Vision Document 2015

My comments for the vision document of MCI:

a. The common entrance test, PG entrance exam right at the end of third professional exams and before internship and a licentiate examn at the end of internship are good steps towards removing some of the deficiencies of the current Medical education system. I highly appreciate them.

b. Duration of MBBS course: The long duration of MBBS course and when coupled with PG course/s is a major deterrent for opting for Medical streams as careers nowadays. This issue has been not looked into. If somehow the duration could be reduced even by one year would be a great achievement. The point to ponder is whether 4 1/2 years are really needed ?

c. Change in nomenclature of Diploma courses to Master of Medicine: In my opinion the change in nomenclature is unwarranted as it will create confusion by having two types of Masters degrees in the field of Medicine. I think changing the fundamental structure of Diploma courses is fine but tampering with the name of the course is a futile exercise which can create confusions later on at the field level and also at the institutional levels. 

d. Career opportunities after PG: It is a very good step to think in lines of creating more career opportunities for the medical students. All the career opportunities have been created after PG of two years duration. I think it would be better if career opportunities are created after MBBS course. This would help the students to focus on their careers right from start. e.g. A student wants to enter into hospital administration after completing MBBS should be given the opportunity to rather than that he/she has to wait for two years further to enter into the career of his choice.

This is in response to the comments invited by MCI for improving the medical education standards in the country. The vision document is available online at

Friday, June 3, 2011

Definition of categories of exposure and use of rabies biologicals

These are the WHO recommended definitions of categories of exposure and use of rabies biologicals:

Category III: -single or multiple transdermal bites or scratches, licks on broken skin, contamination of mucous membrane with saliva (i.e. licks) and suspect contacts with bats: use immunoglobulin plus vaccine

Category II: -minor scratches or abrasions without bleeding or and nibbling of uncovered skin: use vaccine alone

Category I : -touching, feeding of animals or licks on intact skin no exposure therefore no prophylaxis if history reliable