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Data, probability and statistics I · Lesson 06 / 12

Charts that explain rather than hide

A larger bar draws attention. It may represent more records, more minutes or simply a different scale. Read a chart before accepting its story.

Learning paths16 min

Let's discover together

  1. 1

    In the workshop, each bar represents one known delivery duration, and the table contains the same values plus missing ones. The scale begins at zero: bar length represents magnitude. Groups are identified with text, not just color.

  2. 2

    Bars are useful for comparing category counts. To inspect change over time, use time order and a line when appropriate. Joining groups A and B with a line can imply continuity that does not exist.

  3. 3

    Imagine bars for 48 and 50. The difference is 2, not “twice as much”. Cropping the axis near 48 can visually amplify it. Cropped axes can be useful in other chart types when clearly marked; bar lengths require particular care with zero.

  4. 4

    Provide a title/question, unit, count, period and data source. Include the table and a textual conclusion. A beautiful chart does not fix biased collection, missing data or an unsuitable comparison.

Evidence lab

Experiment with fictional deliveries at Aurora station. Analysis runs in this browser. Nothing entered here is sent to the server.

The workshop resets when you leave or reload. Download data and report to keep your work, or send the report to the activity editor, which keeps a draft in this browser. Completion and XP belong to the account.

Header id,group,minutes; one delivery per row; unique id; groups A/B; decimal point; duration 0–1440 with up to two decimal places. Blank means unknown. Up to 100 rows. No quotes or decimal commas. Use invented data.

Selection uses the entered table, including missing values. A draw does not guarantee representativeness. The same seed reproduces selection; it cannot recover cases outside the table.

Make a prediction and analyze the table.

Virtual bag: model with replacement

There are four equally likely tokens; choose how many are blue. Each token returns before the next draw. This is a deterministic simulation, without prizes, money or real observations.

Repeating the seed repeats the sequence. More draws do not guarantee a closer result in every run and do not validate the real-world model.

Two rules, the same accuracy

Ten fictional cases: nine normal and one failure. Rules defined for this example; no AI training or real equipment testing. Same number correct, different consequences.

Two rules, the same accuracy
RuleCorrect / totalMissed failuresFalse alarms

Your investigation report

Official links and next step

✦
YOUR MISSION

Choose a representation and check axes, units and denominators.

Now it's your turn

Discovery workshop

Predict, check, explain

Choose a representation and check axes, units and denominators.
Build your answers and check when you are ready.
A moment to understand

What should accompany a chart so it can be checked?

I need a hint

Choose the representation according to the question. A table and textual explanation help people who use other reading methods.

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Take it with you

Draw 48 and 50 as bars with a visible zero, then make a second representation that exaggerates the difference. Identify the problem and rewrite the caption honestly; do not present the misleading version as evidence.

At your own pace

My files and GitHub

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