Capstone — Build a Concept Manipulative

Capstone · build & submit · about 2–4 hours.

You have spent this course studying IRT through interactive tools — moving sliders to watch ICC curves shift, watching ability estimates update question by question. Now you build one. Pick a single IRT concept and make an interactive web page that teaches it to someone who has never heard of Item Response Theory.

The brief

Build a single-page interactive manipulative that teaches one IRT concept. It must:

let the learner change something (a slider, a button, a text input),
update live as they change it — a curve, a probability, an ability estimate, or a table,
show its output correctly, and
run as a single HTML file that opens in any browser with no install.

Your concept: pick one

Choose a concept you understand well enough to teach. These lend themselves especially well to interactive manipulatives:

Why percent-correct isn't enough (CTT vs IRT) The Item Characteristic Curve (ICC) The Rasch / 1PL model — difficulty Discrimination — the 2PL model Guessing — the 3PL model Ability estimation (EAP / MAP) Item information & test information Calibration — fitting parameters from real response data

One concept, done clearly, beats five done shallowly.

Follow the lifecycle

This is the same build loop from Intro to AI, applied to an IRT concept: plan it → build it → test & submit. The checklist near the bottom tracks these three stages.

How the starter file works

The editor below opens with a working example: two sliders control the difficulty (b) and discrimination (a) parameters of a 2PL item, and the page draws the resulting ICC live as you drag. Read it as three moves:

A control the learner changes: <input type="range"> for b and a.
A computation: the 2PL logistic function P(θ) = 1 / (1 + e^−a(θ−b)) evaluated across the ability range.
A render: draw the curve on a <canvas> so it updates immediately on every input event.

Build it here

Edit the code on the left and it runs live on the right — every change shows instantly, no download needed. It autosaves in this browser as you go.

The code editor needs JavaScript enabled. You can still build your manipulative in any text editor with an AI assistant.

Upload your project files

Your capstone is one HTML file — but if it pulls in extras (an image, a data file, a screenshot for your teacher), upload them all here. Sign in first; only you and your teacher can see these files.

File upload needs JavaScript enabled. You can still Download .html above and submit from your student portal.

Track your progress

This checklist needs JavaScript enabled. The three stages above are the checklist.

Definition of done

Your capstone is complete when it satisfies all of the following criteria:

it conveys a single IRT concept through a functioning, interactive demonstration;
its output is rendered correctly and updates as the input changes;
it is delivered as a self-contained HTML file or a submitted code block;
a classmate who has not taken this course can use it and come away understanding that concept.

Grading rubric (100 points)

Criterion	Points
Interactive — the learner can change the input and the output updates live	30
Mathematically correct — the IRT formula is implemented accurately	30
Pedagogically clear — a newcomer can understand what they are seeing	25
Polished — labels, axis values, and edge cases handled gracefully	15

When you're ready to submit

Click Submit for grading in the toolbar above. Your code is sent to your instructor. You'll receive a score and feedback in your student portal. The passing score for this capstone is 70 / 100.

Written reflection (required)

Before submitting, write a short reflection below. Identify one strength of your manipulative and one thing you would improve with more time. This is part of your grade.

Your reflection is saved automatically to your account when you are signed in and included with your submission.