sequential-monitoring

sequential-monitoring is a skill for Claude Code from clamp-sh/analytics-skills. It costs 185 tokens per session (4,250 once invoked), scanned A, original, MIT.

A statistical method for checking a running A/B test—a comparison between two versions—repeatedly while keeping the planned false-alarm rate.

In plain words
What is it for?
Use it to decide whether a running A/B test has enough evidence to stop, using mixture sequential probability ratio tests or confidence sequences when the test size and timing are suitable.
Why use it?
Looking at test results every day and stopping when they appear successful can create too many false wins; sequential methods account for repeated checks.

Skill for Claude Code

Written for Claude Code: when-to-use in frontmatter.

Part of the analytics-skills plugin — 13 skills shipped together

Good fit Use it to decide whether a running A/B test has enough evidence to stop, using mixture sequential probability ratio tests or confidence sequences when the test size and timing are suitable.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/clamp-sh/analytics-skills/sequential-monitoring
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add clamp-sh/analytics-skills --skill sequential-monitoring
Clone the repo
git clone --depth 1 https://github.com/clamp-sh/analytics-skills

Made for: Claude Code.

Or install analytics-skills, the plugin that ships this one along with the rest of its 13 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for sequential-monitoring

README.md
[![agentmods](https://agentmods.dev/badge/skills/clamp-sh/analytics-skills/sequential-monitoring/github.svg)](https://agentmods.dev/skills/clamp-sh/analytics-skills/sequential-monitoring)
Your own site
<a href="https://agentmods.dev/skills/clamp-sh/analytics-skills/sequential-monitoring"><img src="https://agentmods.dev/badge/skills/clamp-sh/analytics-skills/sequential-monitoring/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for sequential-monitoring

Your own site · 80×15
<a href="https://agentmods.dev/skills/clamp-sh/analytics-skills/sequential-monitoring"><img src="https://agentmods.dev/badge/skills/clamp-sh/analytics-skills/sequential-monitoring.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 185 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,250 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00185 $0.04250
Opus 5 $0.00093 $0.02125
Sonnet 5 $0.00037 $0.00850
Haiku 4.5 $0.00018 $0.00425

Measured 12d ago against content hash 7df46e0f4aed, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

sequential-monitoring scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/sequential-monitoring/SKILL.md · 273 lines

How it starts

The opening of the file, as written. The whole thing — 273 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sequential monitoring

A fixed-horizon A/B test promises a 5% false-positive rate at one planned read. The moment you check the result daily and stop "when it looks good", the actual false-positive rate climbs to 20-30%. Sequential testing fixes this: it lets you check as often as you like and stop the moment the evidence is strong enough, with the type-I error still controlled at the nominal alpha. This skill encodes when to apply mSPRT versus confidence sequences, how to read the boundaries, and when sequential math will not rescue an underpowered test.

When NOT to use this

  • The test has fewer than ~400 exposed users per variant. Sequential methods do not manufacture power. At n<400 the boundaries are nowhere near being crossed and the honest answer is "wait, do not peek".
  • The conversion metric has strong seasonality (B2B day-of-week, retail weekday/weekend, SaaS payday cycles) and the test has not run a full cycle. Sequential boundaries can cross on a Tuesday and uncross by Sunday; the math is valid but the decision is fragile.
  • The user wants to design the test (sample size, MDE, variant logic) rather than read a running one. Different skill.
  • The experiment was already declared with a fixed analysis plan and the team agreed to read it only at the end. Switching to sequential mid-flight is a governance decision, not a stats one; flag it and ask.

The peeking problem

A fixed-horizon test computes a p-value under the assumption you look once, at the planned end. Each additional peek is another chance to cross the 5% threshold by noise alone.

Peeks across the test Actual false-positive rate (nominal 5%)
1 (end only) 5%
2 ~8%
5 (weekly) ~14%
10 (twice weekly) ~19%
Daily over a month ~25-30%

If the user has been "checking how the test is doing" every morning, the nominal 5% threshold is meaningless. They need either a sequential method (always-valid) or alpha-spending (pre-commit to a peek schedule and inflate the threshold).

Read the full file on GitHub · 273 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 273 lines · 185 tokens per session scan A 7df46e0f4aed

Subscribe to this mod's changes

sequential-monitoring is a skill published in the GitHub repository clamp-sh/analytics-skills (8 stars, last pushed 3mo ago), licensed MIT. It adds 185 tokens to every session and 4,250 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.