op-test-trend - Pulse Documentation

name: op-test-trend
description: Mann-Kendall trend test over an ordered numeric series; tier-2 over windowed result rows.
kind: operator
category: TEST
operator: TEST_TREND
type: reference
applies_to: process, compose, predict
examples_tags: [hypothesis-test, tier-2-test, nonparametric, trend-detection, time-series, buffered-pipeline]

Tests emit statistic / p-value / effect size; no Response.Components.

Use when

Checks whether an ordered series, such as monthly totals, tends to keep rising or keep falling.

Questions it answers:

Is monthly churn creeping up?
Has weekly average wait time been falling over the year?

Use something else:

REG_OLS when you want the size of a straight-line slope.
TEST_WELCH when you compare the averages of two specific periods.

Params

alpha — float, default 0.05, in (0, 1).
variant — string, default "mann_kendall" (the only variant).

Field + OrderBy (≥ 1 key) both required. Tier-2 typical — list in Request.PostTests; tier-1 works when the raw field has an ordering key.

multiplicity — optional {method, family}; adds p_adjusted beside the raw p (multiplicity-correction).

Inputs

Field — numeric output column (typically a smoothed window column or a grouped aggregate). OrderBy — numeric or date, defining order.

Output

Statistic = Mann-Kendall Z (S over its SE, continuity-corrected); PValue two-sided normal approx. Details: s, tau, var_s (tie-adjusted), n.

Reading the output

statistic: The Mann-Kendall Z score: the trend count S (details.s) in standard errors, with a continuity correction. Values far from 0 point to a consistent tendency to rise or fall (not necessarily at an even rate).
p_value: a p-value. Below alpha (0.05 unless the request sets another) the result is called significant; that is not the same as important, so read the effect size for how big it is.
details.s: S counts every pair of points: +1 when the later point is higher, -1 when it is lower, 0 when tied.

Gotchas

Never weighted (it reads aggregated result rows, which carry no row weights): any row weight in force on the slot (request, slot or Options.DefaultWeight) is PULSE_WEIGHT_UNSUPPORTED with details.reason; set "weight": null on the slot to run it unweighted.
Meaningful only over an ordered upstream series (a moving average over a date grouper is canonical); reads result rows, not raw cohort.
Empty OrderBy → PULSE_TEST_MISSING_ORDER_BY. Buffered.
n < 3 -> PULSE_TEST_INSUFFICIENT_N; n < 8 warns (advisory; ~10+ advised).
Seasonality-sensitive — pre-deseasonalize (a smoothing window or month grouping).

See

pulse_examples_search tags=[trend-detection]
Skills: statistical-testing, window-design, op-win-moving-avg

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