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# Area under lethality curve

 Author Message    Topic Search   Topic Options mstrange Newbie Joined: 30 Nov 2010 Status: Offline Points: 4 Post Options    Thanks(0)    Quote  Reply Topic: Area under lethality curve    Posted: 01 Dec 2010 at 11:24pm Hi we are interested in knowing more about ways of getting area undr lethal rate curve. Any help appreciated. Sponsored Links Admin Admin Group Administrator Joined: 01 Sep 2009 Location: N. Ireland Status: Offline Points: 394 Post Options    Thanks(0)    Quote  Reply Posted: 02 Dec 2010 at 11:45pm This topic is well-described 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 3-12-2010   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 r-value. 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. Admin Admin Group Administrator Joined: 01 Sep 2009 Location: N. Ireland Status: Offline Points: 394 Post Options    Thanks(0)    Quote  Reply 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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