tests/testthat/test-levene.R

In inferr: Inferential Statistics

context("levene-test")

test_that("output from infer_levene_test matches the expected result", {
  mt <- mtcars
  mt$cyl <- as.factor(mt$cyl)

  k <- infer_levene_test(mt, mpg, group_var = cyl)
  expect_equal(k$bf, 6.4843)
  expect_equal(k$p_bf, 0.0047)
  expect_equal(k$lev, 5.5071)
  expect_equal(k$p_lev, 0.0094)
  expect_equal(k$bft, 6.2047)
  expect_equal(k$p_bft, 0.0057)
  expect_equivalent(as.vector(k$avgs), c(26.66, 19.74, 15.10))
  expect_equivalent(as.vector(k$sds), c(4.51, 1.45, 2.56))
  expect_equal(k$avg, 20.09)
  expect_equal(k$sd, 6.03)
  expect_equal(k$n, 32)
  expect_equivalent(k$levs, c("4", "6", "8"))
  expect_equal(k$n_df, 2)
  expect_equal(k$d_df, 29)
  expect_equivalent(as.vector(k$lens), c(11, 7, 14))
})



test_that("output from infer_levene_test matches the expected result", {
  k <- infer_levene_test(mtcars, mpg, qsec)
  expect_equal(k$bf, 24.3932)
  expect_equal(k$p_bf, 0)
  expect_equal(k$lev, 20.9464)
  expect_equal(k$p_lev, 0)
  expect_equal(k$bft, 22.7064)
  expect_equal(k$p_bft, 0)
  expect_equivalent(as.vector(k$avgs), c(20.09, 17.85))
  expect_equivalent(as.vector(k$sds), c(6.03, 1.79))
  expect_equal(k$avg, 18.97)
  expect_equal(k$sd, 4.55)
  expect_equal(k$n, 64)
  expect_equivalent(k$levs, c("0", "1"))
  expect_equal(k$n_df, 1)
  expect_equal(k$d_df, 62)
  expect_equivalent(as.vector(k$lens), c(32, 32))
})


test_that("output from levene test is as expected", {
  x <- cat("           Summary Statistics
Levels    Frequency    Mean     Std. Dev
-----------------------------------------
  1          24        46.67      10.24
  2          11        51.91      7.66
  3          20        46.8       7.12
  4          145       53.92      10.28
-----------------------------------------
Total        200       52.23      10.25
-----------------------------------------

                             Test Statistics
-------------------------------------------------------------------------
Statistic                            Num DF    Den DF         F    Pr > F
-------------------------------------------------------------------------
Brown and Forsythe                        3       196      3.44    0.0179
Levene                                    3       196    3.4792     0.017
Brown and Forsythe (Trimmed Mean)         3       196    3.3936     0.019
-------------------------------------------------------------------------")

  expect_equivalent(print(infer_levene_test(hsb, read, group_var = race)), x)
})