lab 2 Flashcards
how to know if sample representative of population
unbiased and adequate in size
random sampling
sampling randomly using random number generators etc
systemic sampling
taking samples that have regular arrangement
advantages to systemic sampling
easyer
combination sampling
combination of systemic and random sampling
which sampling method is recommended
random sampling- stat tests based off this
is it better to take more small samples or less large samples?
more small samples
a homogenous area will require
less sampling than a heterogeneous one
highly clumped populations may require
more samples than random or uniform pop
performance curve
plots cumulative mean value of a trait against number of samples taken
how is cumulative mean calcualted
summing the total number of objects encountered and dividing it by total asamples
Quadrat method uses
used for estimating absolute pop density
-used for small sessile or relatively sedentary organisms
mark/ recapture uses
estimating absolute population density
-used for large and or mobile organisms
quadrat process
square shaped sampling area of known/ defined size, count all individuals and extrapolate to entire area
Quadrat variables
n
alpha
A
N
N(hat)
n= average number sampled in quadrats
alpha= size of quadrat
A= total area
N=total pop size
N hat=estimated total pop size
N(hat) when do you round
when there is a decimal, always round
Mark recapture process
capture sample of individuals, mark, release into pop allow to disperse
recapture random sample, note # of marked and unmarked
Assumption of mark recapture
marks must not be lost or overlooked
no change in ration of marked to unmarked animals as a result of birth, death, immigration or emigration
-marked and unmarked similar in all aspects- trappability etc
-probability for recapture equal for marked and unmarked
Mark recapture variables
M
m
N
n
M=total number marked in population
m=number marked in sample
N=total population size
n=total number in the sample
