The data analysis of IFR vs Age of the population shows a significant correlation ( r ) of Sigmoid model ( 3-5 )** .** Then this mean dataset **( Figure – I )** is analysed by best -fit software like of which Logistic regression shows a significant correlation coefficient ( r ) [ 0 < r < 1.0 ] with tolerable std.error ( s ) , Cov ( Matrix ) and residual table of the Parametric statistics . A part from regression analysis a PIE chart of the dataset is also shown as bellow. The sigmoid function results from the analysis can be represented as follows **( Figure – II )** .

** **Y ( IFR ) = Sigmoid f [ X ( Age ) ] = [ a / ( 1 + b* exp ( -cx ) ] --------**eqn( 1 )**

a , b , c are the coefficients obtained from best fit analysis [ 5 ]

By expanding [ e^ ( -x ) ] series we can get the modified equation as follows :

exp ( - cx ) = 1- cx + c^2 / 2! + c ^ 3 / 3! - ..................... approx = ( 1- bcx ) ----------------**eqn ( 2 )**

So **eqn ( 1 )** can be simplified as Y = a( 1- bcx ) ^( -1 ) = a ( 1 + bcx – b c^2x^2 + b c^3 x ^ 3 +............)

approx = a ( 1 + bcx – bc^2x^2 ) ----------------------( **eqn 3 )**

From **eqn ( 3 )** one can simplify the Y ( IFR ) is a second order quadratic polynomial fit of

X ( Age ) .

The **eqn ( 1-3 )** represents the desired model equation and the measure of a sigmoid probability

( 3,5) of fatality rate of Covid -infection with age of the patients . A simplified Excell representation

ie Pie chart also supports the sigmoid distribution . **eqn ( 3 )** also represents the sigmoid probability

can be also approximately represented as quadratic fit .