CHAPTER 



14 



Calculation of Data 



Experimental data are meaningful only if they can be compared to 

 some standard of reference and if general interpretations can be drawn 

 from them. In all the sciences it has become customary to express data 

 in certain sets of standard terms, just as the chemist expresses an amount 

 of gas as the volume it would occupy at 0° C and 760 mm Hg. Biologists, 

 whose materials are nonstandard, naturally have greater difficulty stand- 

 ardizing their figures. A chemist can speak of concentrations of solutions 

 in moles per liter, but what is the concentration in moles per liter of the 

 potassium ions in a single cell? Or what is the concentration in moles per 

 liter of the Chlorella cells in a Warburg manometer flask? 



Biologists must carefully specify the exact conditions under which a 

 measurement was made if there is to be any hope of repeating the meas- 

 urement. This can be accomplished by carefully detailed descriptions, 

 but it can be done somewhat more simply by a careful choice of units 

 in which to express results. 



Amounts of biological material 



If a 20-Kg dog eats 1 Kg of food a day, two 20-Kg dogs should eat 

 about 2 Kg. In many instances such relationships hold reasonably well. 

 Most of the computations expressed in this section are based on the 

 assumption that the magnitude of an effect is directly related to the 

 amount of biological material. Unfortunately, a 40-Kg dog is not likely 

 to eat the same amount as the two smaller dogs for a variety of reasons. 

 The assumption made above must be used with considerable care. 



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