An S7 class produced by JT_TEST pipelines using statim::x_by as the
variable mapper <var_id>.
Inherits from statim::class_stat_infer, so statim::auto_tidy()
dispatches on it automatically. Downstream packages can use it as a
parent in S7::new_class().
Details
Only vars, statistic, p_value, and alternative are guaranteed
by every constructor of class_jt_test. z_score, mean, and
variance are optional and, when supplied, join the headline summary
table on print(); when absent, they're left out of that table
entirely rather than shown as "Not given". approximate and
method are also optional, and appear in a second details table,
printed as "Not given" when a constructor doesn't supply them. The
x_by baseline path always populates all eight, since
jonckheere_terpstra_test() returns them unconditionally.