skill~210 mindifficulty

Data Cleaning

Analysts spend most of their time cleaning data, and dirty data silently ruins every downstream chart and conclusion.

1

Learn it

Cleaning means making data trustworthy: deciding whether to drop or fill missing values, fixing inconsistent categories and typos, parsing dates into real date types, and resolving encoding issues. It is judgment as much as technique, because each fix encodes an assumption. A reproducible cleaning workflow beats one-off manual edits.

By the end you’ll be able to

  • Handle missing values and inconsistent entries
  • Standardize types, dates, and text encoding

Free resources

2

Practice

Take a messy real-world dataset, document each problem, and apply fixes for missing values, inconsistent text, and mis-typed dates.

3

Build it — your output

A cleaned dataset plus a short log of every cleaning decision and its rationale.

4

Prove it — check yourself

You’re ready to move on when you can honestly say yes to each:

  • Can you choose between dropping and imputing missing values with justification?
  • Can you standardize inconsistent categorical entries?
  • Can you parse and validate date and encoding problems?

Do it with AI

Use a free AI tool as your tutor and pair-programmer. Copy a prompt below into Claude, ChatGPT, or Gemini (for building, try Cursor or Copilot).

The habit: Try it yourself first — a little struggle is where the learning actually happens. Then ask for a hint before the answer — never copy blindly.

  • Understand itClaude / ChatGPT / Gemini

    I'm a beginner learning "Data Cleaning". Explain it in simple terms with a real-world analogy, then ask me ONE question to check my understanding — don't reveal the answer.

  • PracticeClaude / ChatGPT / Gemini

    Give me 3 short practice problems on "Data Cleaning" (my goal: handle missing values and inconsistent entries), from easy to hard. Don't include the solutions yet — I'll try them first, then ask you to check.

  • Get unstuckClaude / ChatGPT / Gemini

    I'm stuck on this exercise about "Data Cleaning": [paste your attempt here]. Give me ONE small hint to move forward — do NOT give me the full solution.

  • Build & reviewCursor / Copilot

    Here is my work for a "Data Cleaning" task: [paste your code or answer]. Review it: point out what's wrong and WHY, and suggest improvements — but let me make the fixes myself.

  • Prove itClaude / ChatGPT / Gemini

    Quiz me on "Data Cleaning". Ask me 5 questions one at a time, wait for my answer each time, then tell me if I'm right and briefly why.

My notes