Performs a test of sphericity on a dataframe with multiple measures, one subject per line. It assesses the significance of the null hypothesis that the covariance matrix is spherical. This test is described in (Abdi 2010)
MauchlySphericityTest(dta, cols)A data frame containing within-subject measures, one participant per line;
A vector indicating the columns containing the measures.
p the p-value of the null hypothesis that the data are spherical.
Abdi H (2010). “The greenhouse-geisser correction.” Encyclopedia of research design, 1(1), 544--548.
# creates a small data frames with 4 subject's scores for 5 measures:
dta <- data.frame(cbind(
col1 <- c(3., 6., 2., 2., 5.),
col2 <- c(4., 5., 4., 4., 3.),
col3 <- c(2., 7., 7., 8., 6.),
col4 <- c(6., 8., 4., 6., 5.)
))
# performs the test (here p = 0.5824)
MauchlySphericityTest(dta)
#> [1] 0.5824426