Title: Week 12 — the fine print at the bottom of every poll is about to be yours
Course: Introduction to Statistics (18-Week Generic Edition)

Hi everyone,

Quick experiment: find any poll in your news feed this week. Somewhere near the bottom it says "margin of error ±3 percentage points." You've scrolled past that sentence a hundred times. By the end of this week, you'll be able to recompute it from the article's own numbers — in six spreadsheet cells — and you'll know the two things it quietly doesn't cover.

This week — Confidence Intervals for a Proportion — the machine you built last week gets its most public job. Last week: intervals for a mean, with the t-multiplier. This week: the same estimate ± reach anatomy for percents — renewal rates, recycling rates, return rates, poll numbers — with the z-multiplier and just three numbers to remember (1.645, 1.96, 2.576).

Three things not to miss: 1. Chapter 12 is your primary reading — the whole build lives there, including the z table and the sample-size formula. Start there; everything else gets easier. 2. Data Lab 12 — "Anatomy of a Poll" — you'll audit a real published poll's margin of error (or the provided one) and check whether its fine print survives your recomputation. Due at the end of Week 12. 3. Discussion 12 — "The 400 vs. 18,000 Problem" — a random sample of 400 says 62%; an opt-in app poll of 18,000 says 44%. Which should the city council believe? Initial post is due two days before the week ends*, so classmates have time to reply.

Plus the usual rhythm: Tutorial 12 (your AI tutor — share link + summary), the ungraded practice set, Quiz 12 (closed to AI), and Assignment 12 — "The Honest Percent" (AI-coached, best attempt counts). All due at the end of Week 12.

One heads-up from the future: next week someone walks in with a specific claim — "our support is 60%" — and we test whether it's plausible. The interval you master this week is the doorway to hypothesis testing.

Open the Start Here / Module Overview page first — it lays out everything in order with due points. Bring one poll from your own feed to the first session; we'll put its fine print on trial.

See you in the course!