T-Test

TTEST() performs a t-test for one-sample, two-sample, paired, pairwise, or formula-based comparisons.

Usage

TTEST(.model = NULL, .data = NULL, ...)

Arguments

.model

A model ID from x_by(), pairwise(), or a formula. When supplied, the test executes immediately. When NULL (default), returns a test_spec for use in the pipeline via prepare_test().

.data

A data frame. Only used on the standalone path.

...

Additional arguments passed to the implementation: .paired, .mu, .alt, .ci for the classical path.

Value

An htest_spec object (standalone or eager), or a test_spec object (pipeline).

Supported model IDs

• x_by() — two-sample or paired t-test

• pairwise() — pairwise t-tests across variables

• formula — one-sample or two-sample t-test

Method variants (via via())

• "boot" — bootstrap confidence interval

• "permute" — permutation test

• "permute_rfast" — permutation test backed by Rfast2

Examples

# eager
TTEST(x_by(extra, group), sleep)
#> -- Summary ---------------------------------------------------------------------
#> 
#> ─────────────────────────────────
#>   groups   diff   t-stat  pval   
#> ─────────────────────────────────
#>   group   -1.580  -1.861  0.079  
#> ─────────────────────────────────
#> 
#> 
#> -- Confidence Interval ---------------------------------------------------------
#> 
#> ──────────────────────────────
#>   groups  lower_95  upper_95  
#> ──────────────────────────────
#>   group    -3.365    0.205    
#> ──────────────────────────────
#> 
#> 

# pipeline
sleep |>
    define_model(x_by(extra, group)) |>
    prepare_test(TTEST) |>
    conclude()
#> 
#> == Model ======================================================================= 
#> 
#> Model ID : x_by 
#> Args : extra | group 
#>     x_vars : 1 
#>     by_vars : 1 
#> 
#> == T-Test ====================================================================== 
#> 
#> -- Summary ---------------------------------------------------------------------
#> 
#> ─────────────────────────────────
#>   groups   diff   t-stat  pval   
#> ─────────────────────────────────
#>   group   -1.580  -1.861  0.079  
#> ─────────────────────────────────
#> 
#> 
#> -- Confidence Interval ---------------------------------------------------------
#> 
#> ──────────────────────────────
#>   groups  lower_95  upper_95  
#> ──────────────────────────────
#>   group    -3.365    0.205    
#> ──────────────────────────────
#> 
#> 

# bootstrap
sleep |>
    define_model(x_by(extra, group)) |>
    prepare_test(TTEST) |>
    via("boot", n = 2000) |>
    conclude()
#> 
#> == Model ======================================================================= 
#> 
#> Model ID : x_by 
#> Args : extra | group 
#>     x_vars : 1 
#>     by_vars : 1 
#> 
#> == T-Test · boot =============================================================== 
#> 
#> ============================== Bootstrapped T-test =============================
#> 
#> 
#> -- Summary ---------------------------------------------------------------------
#> 
#> Warning: running command 'tput cols' had status 2
#> ------------------------------
#>   CI     :   [-3.21, 0.0702]
#>   n_reps :              2000
#> ------------------------------
#> 
#> 

# permutation
sleep |>
    define_model(x_by(extra, group)) |>
    prepare_test(TTEST) |>
    via("permute", n = 2000) |>
    conclude()
#> 
#> == Model ======================================================================= 
#> 
#> Model ID : x_by 
#> Args : extra | group 
#>     x_vars : 1 
#>     by_vars : 1 
#> 
#> == T-Test · permute ============================================================ 
#> 
#> ============================== T-test Permutation ==============================
#> 
#> 
#> -- Summary ---------------------------------------------------------------------
#> 
#> ───────────────────────────────
#>   Statistic  p-value  n_perms  
#> ───────────────────────────────
#>    -1.580     0.092    2000    
#> ───────────────────────────────
#> 
#>