# Edps/Psych/Soc 584
# Fall 2018
# C.J.Anderson
#
# UofI Admissions Scandel (2 x 2 table)
# The data were from White's e-mail.
#
# Part of the argument that White made was that the general admission rate was 69% and
# the rate on the I List was higher but it only lead to only additional 13 students being
# admitted.
#
# 160 students on the I list
# 123 admitted
# 76.88% admitted from I list
#
# 69% of 160 = 110.... so 123 - 110 = 13 (i.e., number admitted from I list minus 69% is 13)
#
library(Epi) # for twoby2
library(MASS) # for loglm
library(vcd) # for assocstats
# create data frame
var.levels <- expand.grid(admit=c("yes","no"), Ilist=c("Ilist","General"))
( scandel <- data.frame(var.levels, count=c(123, 37, 18000 , 8000) ) )
# tabular form
scandel.tab <- xtabs(count ~ admit + Ilist, data=scandel)
addmargins(scandel.tab)
# data should be in matrix form -- this keeps row & column names and level values
( scandel.mat <- as.matrix(scandel.tab) )
# Compute differences, relative risk & odds ratio, including CIs
twoby2(scandel.mat)
# Chi-square test statistics: data frame (case data)
loglm(count ~ admit + Ilist, data=scandel)
# or --- this includes Yate's correction for continuity, which isn't used much anymore
chisq.test(scandel.tab)
# or
ax <- as.factor(scandel$admit)
ix <- as.factor(scandel$Ilist)
glm(count ~ ax + ix, data=scandel, family=poisson)
# or
assocstats(scandel.tab)