Biostatistics Part 1 PSM Videos

This is an animated lecture video on " BIOSTATISTICS " chapter from the PARK TEXTBOOK of COMMUNITY MEDICINE.


Hi..........welcome to abmbbs.......Now the basic Biostatistics needed in mbbs can be divided into these broad headings.I will be dealing with the first 3 in this video.The next 4 topics will be covered in a 2nd video.The remaining extra topics will be covered in a 3rd video.
So...the first topic is data presentation.......we all know that data can be subdivided into 2 categories...Quantitative & qualitative.So now we will discuss about the various ways to present quantitative data.....

1st is HISTOGRAM.....a histogram is a graphical presentation for continuous quantitative data....the continuous groups are plotted on the X axis & the frequencies are marked on the Y axis.

Next come FREQUENCY POLYGON.....it is similar to a histogram except that it is made by joining mid points of class intervals at the heights of frequencies.

Next is FREQUENCY CURVE....it is basically a frequency polygon that has a large number of observations & reduced group intervals.....hence the angles are smoothened & it becomes a curve.

Next is a LINE CHART....its also known as LINE GRAPH....it shows the trend of an event over time.

Next is CUMULATIVE FREQUENCY DIAGRAM...its also called OGIVE....it is a graph of cumulative relative frequency distribution.

Finally there's the SCATTER DIAGRAM or DOT DIAGRAM.....its also called CORRELATION DIAGRAM.....because , it is used to depict correlation between 2 variables....I will be coming back to SCATTER DIAGRAM in a minute......This brings us to the end of the quantitative methods of data representation.....Now we talk about the Qualitative methods of data representation.

First is BAR DIAGRAM.....it is used for visual comparision of magnitude of different frequencies.....it is considered to be the most versatile of all statistical diagrams..

Next comes....PIE or SECTOR DIAGRAM.....here, the categories are represented as a percentage of the total 100%....But remember , for pie diagrams...all the pie categories must be mutually exclusive...

Next there's PICTURE DIAGRAM or PICTOGRAM.....it is a method of data representation for the common man to understand...so it often contains pictures....

Finally there's MAP DIAGRAM or SPOT MAP......it is prepared to show geographical distribution of frequencies.Here each dot marks 1 frequency......this completes the methods of data representation.....Now ,coming back to SCATTER DIAGRAM.......we have understood that it is used to depict correlation.....but how???...... look at the diagram of the left....here the dots are arranged in such a manner that their average forms a straight line whose slope is positive.....this slope is the CORRELATION COEFFICIENT 'R'.....when the CORRELATION COEFFICIENT 'R' =+1.....then it is called positive correlation..........now.... look at the diagram in the middle...here ,,the dots are arranged in such a manner that their average forms a straight line , whose slope is negetive.....so R=-1 & the correlation is said to be negetive........finally,,...look at the diagram on the left...here, no straight line can be drawn , because the dots are arranged diffusely....so there is no correlation...


Next we come to the topic of variables....a variable is a character or attribute that varies from person to person & from time to time.......so...variables can be divided into Quantitative & Qualitative variables....QUANTITATIVE Variables are the ones that can be measured directly on a metric scale....example..weight, height, Mid arm circumference........QUALITATIVE Variables are the ones that cannot be measured....hence they have a nominal scale...typical examples include ABO blood group, sex & type of anaemia.......If you are wondering what is a nominal scale ,,,dont worry...i will be discussing the types of scales in a minute.....

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