#Biostatistics 420

#CHI-SQUARE TEST FOR GOODNESS OF FIT
#ZAR EXAMPLE 22.8
ZAR=read.table("ZarEX22.8R.txt")
ZAR
attach(ZAR)

chisq.test(observed,p=expected,rescale.p=TRUE)

#G-TEST FOR GOODNESS OF FIT
#APPROPRIATE TEST FUNCTION NOT YET FOUND IN R
#THEREFORE, I HAD TO DO THIS FROM SCRATCH:

#G STATISTIC:
G=2*sum(observed*log(observed/expected))
G

#CRITICAL VALUE:
alpha=0.05
k=4
g=0
df=k-g-1
C=qchisq(1-alpha,df)
C

#PROBABILITY:
P=(1-pchisq(G,df))
P

#YATES CORRECTION:
ZAR2=read.table("ZarEX22.1R.txt")
ZAR2
attach(ZAR2)
df=1

#YATES CORRECTED G STATISTIC:
obs=c(84-0.5,16+0.5)
Gc=2*sum(obs*log(obs/expected))
Gc

#YATES CORRECTED PROBABILITY:
Pc=(1-pchisq(Gc,df))
Pc