mean- -The arithmetic mean (simple average) of a sample is the most 

 frequently used estimator of the true population mean y. A bar 

 over a symbol customarily denotes an average; that is, 



X = arithmetic mean of X 



zx 



X = 



number of values 



median—That value of a variable (in an ordered array) that has an 

 equal number of items on either side of it. 



nonparametric method--A statistical test that is not concerned with 

 the specific parameters, but rather with the distribution of the 

 variates. Also referred to as distribution free. See parameter. 



oscillatory — Having a periodic motion backward and forward or vibrating 

 or varying above and below a mean value. 



parameter—A parameter is a measurable characteristic of a population. 

 The mean is an example of a parameter. 



patchiness--The clumped distribution of individuals, in which distribution 

 is not random and the variance is significantly greater than the mean 

 value, also referred to as aggregation or clustered distribution. 



population—The .population is the total number of individual observations 

 about which inferences can be made. The population can exist anywhere, 

 but it is limited in space and time. 



quadrat— A quadrat is a plot used for ecological or population studies. 

 It may be square, rectangular or circular. Areas of quadrats are 

 commonly 0.1, 0.5, and 1.0 square meters. 



random — A single element is randomly drawn from a population if that 

 element was selected by any procedure that gives every element in 

 the population an equal chance of being drawn. 



replicates — Repeated samples from the same population. Replication is 

 necessary to detect residual variation and to detect smaller and 

 smaller deviation among means. 



rose bengal dye--A bluish-red acid dye used as a biological stain to 

 aid in sorting the animals from the sediment. 



sample— Any subset of a population is called a sample of that population. 



Shannon- Weaver Index- -The purpose is to find the diversity (H") in 

 large sampled communities. The function is: 



N. N. 



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