Area under lethality curve 
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Admin
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Posted: 07 Apr 2011 at 11:23pm 
If you are interested in this topic you might find the post at http://dairyscience.info/forum/topic260_post1109.html#1109 of some interest comparison of Fo values obtained using 3 numerical integration methods (trapezoidal, Simpson's and Romberg rules)
and 7 data sets.


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Admin
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This topic is welldescribed in older textbooks e.g. counting "squares" under the curve and dividing this number by the number of squares in the rectangle obtained by plotting a lethality value of 1 for 1 minute. Similarly a planimiter can be used to obtain the area under the curve which is divided by the area (determined using the planimiter) of the the rectangle obtained by plotting a lethality value of 1 for 1 minute. It is also possible to cut out the areas, weight them and to divide the weight of the smaller area into the weight of the larger one to obtain the F value at the reference temperature. However, it is very easy to do this calculation using a spreadsheet and numerical integration.
I will say a little more about this when I get some more time.
Additional material added 3122010
Area can be calculated using the trapezoidal rule (also known as the trapezoid rule) or Simpson's rule. The free F calculator on this site uses the trapezoidal rule to calculate area under lethality time curve. You can also download a spreadsheet to do the calculation.
Another option is to use Excel to calculate the trend line, the equation (use the polynomial option, order 2) for the curve and the rvalue. If the r value is >0.9 you could consider integrating the equation if your knowledge of calculus is good. WolframAlpha can be used to check your calculation.


mstrange
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Hi we are interested in knowing more about ways of getting area undr lethal rate curve. Any help appreciated.


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