Cochran's Q test

COCHRAN_QTEST() tests whether the distribution of a continuous variable differs across the levels of one or more grouping variables. It is the rank-based, distribution-free analogue to one-way ANOVA. If COCHRAN_QTEST is supplied within the lazy-loaded pipeline, supply COCHRAN_QTEST as a function i.e. prepare_test(.test = COCHRAN_QTEST).

Usage

COCHRAN_QTEST(.var_id = NULL, .data = NULL, ...)

Arguments

.var_id: A variable mapper <var_id>. Currently supports x_by(). When supplied, the test executes immediately. If .var_id maps multiple grouping variables, one Kruskal-Wallis test runs per grouping variable against the same continuous variable.
.data: A data frame. Only used on the standalone path.
...: Additional arguments passed to the implementation. See the Supported variable mapper section for the full list per path.

Value

A cld_exec object (in statim::conclude()), a stat_infer_spec object, or a test_spec when .var_id = NULL. cqtest_def_xby's baseline returns a class_cq_test object by default; its pairwise variant instead returns a plain list (COCHRAN_QTEST, comps) with its own print method. cqtest_def_on's baseline returns a plain list (statistic, df, p_value) with its own print method — neither path shares a class between them.

Details

H0: all samples come from the same distribution (equal medians, under the assumption of equal shape). H1: at least one sample is stochastically greater than another.

Supported variable mapper `<var_id>`s

x_by(): grouped Kruskal-Wallis test, with optional pairwise comparisons. See details from cqtest-xby.

Examples

set.seed(123)
x = sample(0:1, 45, replace = TRUE)
treatment = gl(3, 1, 45, labels = c("A", "B", "C"))
block = gl(5, 3, 45, labels = 1:5)
COCHRAN_QTEST(x_by_b(x, treatment, block))
#> -- Summary ---------------------------------------------------------------------
#> 
#> ─────────────────────────────────────────────────
#>     vars     n_groups  Q statistic  df  p_value  
#> ─────────────────────────────────────────────────
#>   treatment     3         1.500     2    0.472   
#> ─────────────────────────────────────────────────
#> 
#> 
#> -- Frequency Table -------------------------------------------------------------
#> 
#>                           Cross Tabulation:   by Value
#>                           ───────────────────────────
#>                                     Value     
#>                           ───────────────────────────
#>                                     0    1    TOTAL  
#>                           ───────────────────────────
#>                             A       7    8     15    
#>                           
#>                             B       10   5     15    
#>                           
#>                             C       9    6     15    
#>                           ───────────────────────────
#>                             TOTAL   26   19    45    
#>                           ───────────────────────────
#>