CHAPTER XLI 



STATISTICAL METHODS IN PROTOZOOLOGY 



By 

 Lowell J. Reed 



The Johns Hopkins University School of Hygiene and 

 PubHc Heahh 



The statistical method has made its entry into the various 

 fields of biology through a desire on the part of the vv^orkers 

 in these fields to add a quantitative element to their qualitative 

 descriptions. This has usually resulted in a few early experiments 

 and papers giving a simple set of measurements on some particular 

 characteristic, usually the size of a biological organism. At the 

 start, such measurements have been given individually and it 

 is only after the accumulation of a series of such measurements 

 that a real need for the statistical method is felt. The introduc- 

 tion of the statistical method into any particular field for the 

 purpose of simple description of size is quickly followed by its 

 use for the purpose of describing more complex characteristics, 

 such as biological variability, relationship between variables and 

 rates of change with time. The field of protozoology has, in 

 recent years, been following the natural course of evolution 

 with regard to the statistical method, and it is the purpose of 

 this article to present certain elementary statistical procedures 

 and to point out their applicability in the field of protozoology. 



STATISTICAL DESCRIPTION OF MEASUREMENTS ON A SINGLE 



VARIABLE 



When measurements are taken on a single variable and they 

 are few in number, it is a perfectly satisfactory logical process 

 to record these measurements and treat them individually. When, 

 however, we have taken a large number of such measurements, 

 we find that this process cannot be followed, for the mind fails 



439 



