R Chi-square tests

Chi-square tests

Working Directory

setwd("/Volumes/EDMS451/Summer 2021/Software Instructions")

Manually Enter Data

dat <- data.frame(group1 = c(76, 28, 34, 14),
                  group2 = c(32, 15, 24, 7))
rownames(dat) = c("type1", "type2", "type3", "type4")

dat                           # view the data

      group1 group2
type1     76     32
type2     28     15
type3     34     24
type4     14      7

Chi-square test of goodness of fit

obs <- rowSums(dat)
exp <- c(.60, .14, .16, .10)

test_gof <- chisq.test(obs, p = exp)
test_gof            #test results

    Chi-squared test for given probabilities

data:  obs
X-squared = 22.531, df = 3, p-value = 5.057e-05

Chi-square test of independence

test_ind <- chisq.test(dat)
test_ind$expected   #expected frequency

        group1    group2
type1 71.37391 36.626087
type2 28.41739 14.582609
type3 38.33043 19.669565
type4 13.87826  7.121739

test_ind$observed   #observed frequency

      group1 group2
type1     76     32
type2     28     15
type3     34     24
type4     14      7

test_ind            #test results

    Pearson's Chi-squared test

data:  dat
X-squared = 2.348, df = 3, p-value = 0.5034