Statistical Inference vs Quarry

Statistical Inference is an independent study app built for students, self-learners, analysts, and anyone reviewing core inference ideas through focused practice. Work through 160 questions across Fundamentals, Practical Skills, Common Pitfalls, and Advanced Concepts. Each question includes an explanation so you can understand why an answer works, not just whether you got it right. Features: - FSRS spaced-repetition intervals to help reviews land at the right time - Weak-point heatmap to show where you need more practice - Daily challenge for consistent study - Mock exams for timed review - Offline practice for commutes, classrooms, and low-signal moments - No login required Use it to review estimation, confidence intervals, hypothesis testing, p-values, sampling distributions, power, errors, likelihood ideas, and common interpretation traps. Practice offline, no login required. Independent study app for Statistical Inference practice. Not affiliated with, endorsed by, or sponsored by any company, certification body, exam operator, or vendor. All trademarks belong to their respective owners.

Quarry is a focused, offline gym for data and coding interviews. 108 hand-picked problems across SQL, pandas, and Python — write real code, run it on your device, and get graded instantly. Everything runs on-device. The SQL and Python engines are built into the app, so there's no sign-up, no internet requirement, and nothing you write ever leaves your phone or iPad. Practice on a plane, on the subway, or anywhere. WHAT'S INSIDE • 108 problems across three tracks: SQL queries, pandas data wrangling, and Python algorithms & data structures. • Real execution, real grading. Your output is checked against the expected result — no self-marking. • Company tags. Filter problems by the company you're interviewing at. • Hints and full solutions when you're stuck. • Difficulty levels from Easy to Hard, grouped by topic. • A free-form Playground for scratch SQL and Python. • Universal app — designed for both iPhone and iPad. PRIVATE BY DESIGN No accounts. No analytics. No ads. No tracking. Quarry collects nothing and works fully offline. Whether you're prepping for a data analyst, data engineer, data scientist, or software role, Quarry gives you a quiet, fast place to actually practice.