levene_test | R Documentation |
This function performs the Levene's test for equality of variance.
levene_test(data = NULL, x, groups, alpha = 0.05, modcv = FALSE)
data |
a data.frame |
x |
the variable in the data.frame or a vector on which to perform the Levene's test (usually strength) |
groups |
a variable in the data.frame that defines the groups |
alpha |
the significance level (default 0.05) |
modcv |
a logical value indicating whether the modified CV approach should be used. |
This function performs the Levene's test for equality of variance. The data is transformed as follows:
w_{ij} = \left| x_{ij} - m_i \right|
Where m_i
is median of the ith
group. An F-Test is then
performed on the transformed data.
When modcv=TRUE
, the data from each group is first transformed
according to the modified coefficient of variation (CV) rules before
performing Levene's test.
Returns an object of class adk
. This object has the following fields:
call
the expression used to call this function
data
the original data supplied by the user
groups
a vector of the groups used in the computation
alpha
the value of alpha specified
modcv
a logical value indicating whether the modified
CV approach was used.
n
the total number of observations
k
the number of groups
f
the value of the F test statistic
p
the computed p-value
reject_equal_variance
a boolean value indicating whether the
null hypothesis that all samples have the same variance is rejected
modcv_transformed_data
the data after the modified CV transformation
“Composite Materials Handbook, Volume 1. Polymer Matrix Composites Guideline for Characterization of Structural Materials,” SAE International, CMH-17-1G, Mar. 2012.
calc_cv_star()
transform_mod_cv()
library(dplyr)
carbon.fabric.2 %>%
filter(test == "FC") %>%
levene_test(strength, condition)
##
## Call:
## levene_test(data = ., x = strength, groups = condition)
##
## n = 91 k = 5
## F = 3.883818 p-value = 0.00600518
## Conclusion: Samples have unequal variance ( alpha = 0.05 )
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