LOGISTIC REGRESSION

Logistic Regression

EXAMPLE: Seedling Survival: It Really is a Jungle Out There!

Tropical rain forests have up to 300 species of trees per hectare, leads to difficulties when studying processes which occur at the community level. To gain insight into species responses, a sample of seeds were selected from a suite of eight species selected to represent the range of regeneration types which occur in this community. This representative community was then placed in experimental plots manipulated to mimic the natural variation in light conditions found in rain forests. Mammals were excluded from one half of each plot in order to assess their effects on the regeneration of rain forest trees. The two questions of specific interest are:

Are species different in their probabilities of establishing across the environmental mosaic of the forest?

How do these species properties interact with the manipulated variables to influence establishment probabilities?

SURV: Survival -- {No = 0, Yes = 1} of seedling
GAP: {0, 1} Indicator for understory versus clearing
CAGE {0, 1} (0 = Absent, 1 = Present} Enclosure to prevent mammals from eating the seeds
LITTER: (different levels = 0,1,2,i)

SPECIES = (a,b,g,h,i,m,r,s), 1 smallest 8 largest E = Epigeal - cotyledons, H=Hypogeal - reserves in seed

a       Ardisia       3 H     
b       C. biflora    7 H     
g       Gouania       1 E
h       Hirtella      8 H
i       Inga          4 H 
m       Maclura       2 E
r       C. racemosa   6 H
s       Strychnos     5 E

HANDOUTS:

Definitions of dummy variable coefficients

ANALYSIS of Deviance table and Parameter estimtes

residual plot