AIIMS MD MS Exam May 2010 Notification

The Indian Express March 07 2010  

 

Community Medicine - Points to be noted Part 3 - BIOSTATISTICS

BIOSTATISTICS

1. The more prevalent a disease, the more will be it's P.P.V..i.e., less will be it's False Positives. Less prevalent 

     more false positives.

---- As prevalence Increases --- PPV Increases ---- False +ve Decreases.

---- As prevalence Decreases -- PPV decreases ---- False +ve Increases.

2. Standard Deviation

If values are same as mean, then SD = 0.

3. The NORMAL Distribution

The probability of a reading to fall outside 2 SD is 5% ie., 5/100 = 1/20 = 0.05.

Normal Curve

-----------------------

Mean = Median = Mode = 0.

S.D = 1.

Area = 1.

No: of Observations - Infinite.

Relative Deviate or Standard Normal Deviate (Z)... Z = (x - Mean) / SD.

Z------> The distance of a value 'x' from Mean, in Normal curve, in terms of SD is called as RD/SND/Z.

4. Determinants of causality - Criteria is Bradford- Hill Criteria.

It does not include Concurrency.... ie., the cause and effect need not be present simultaneously.

Criteria includes.... 1. Temporal Sequence     2. Biological Gradient  3. Strength of Association etc.

5. Two variables can be simultaneously plotted in scatter plot diagram / Correlation Diagram.

6. Degree of Freedom = (c-1) x (r-1), where 'c' is the number of columns and 'r' is the number of rows. 

Note : Although this is the usual formula used, there is exception. Please check it.

7. Random / Probability Sampling is used in Inferential Statistics

        Are of following types--

                      1. Simple Random Sampling - 

                      2. Stratified Random Sampling - Population is stratified into internally homogenous 

                                                                         groups...Population ---> Village and Town.

                                                                         Into Hindus and Christians.

                      3. Cluster Sampling - When Sample size is Very large.

                      4. Systematic Sampling - for eg:- Every 3rd person admitted in a Hospital.

8. Standard Error of Mean = S.E. = Standard Deviation / Sq.rt of 'n'.

    So in Random sampling, if sample size is increased, the Standard Error would decrease.

"If a scientist reads two articles each day
from the world’s scientific literature
published that day, at the end of one
year the scientist will be 60 centuries
behind in keeping up with the current
scientific literature. To keep current
with the literature, the scientist would
have to read 6000 articles each day."

Quoted from Medical Imaging Physics. 4th Edition, 2002.

Community Medicine - Points to be noted Part 2

For Part 1 : CLICK HERE


16. Indian Red Cross Act - 1920.

17. SIDA - Swedish International Development Agency - NTCP (T.B).

18. DANIDA - NBCP.