Rullst AcademyRullst Academy/Lesson
Data, probability and statistics I · Lesson 03 / 12

How many — out of how many?

One route met six deadlines; another met 12. Without knowing how many deliveries each attempted, we cannot yet compare proportions.

Learning paths16 min

Let's discover together

  1. 1

    An absolute frequency is a count. A relative frequency divides that count by the relevant total. If six of eight deliveries arrived within five minutes, the proportion is 6/8 = 0.75 = 75%.

  2. 2

    Twelve out of 20 is 60%. The second route has more on-time deliveries as a count but a smaller proportion. “More” must specify which measure is compared.

  3. 3

    The workshop defines on-time as minutes ≤ 5. Its percentage uses known durations only. In B, five out of five known durations meet the deadline; the sixth is unknown. “100% of known cases” is not “100% of all six deliveries”.

  4. 4

    Keep the count, denominator and rule beside the percentage. A cell with no known observations shows “no data”, not 0%. Do not add percentages from unequal groups as if they were counts.

Evidence lab

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

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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

Build frequencies and proportions with an explicit denominator.

Now it's your turn

Discovery workshop

Predict, check, explain

Build frequencies and proportions with an explicit denominator.
Build your answers and check when you are ready.
A moment to understand

Which comparison uses totals correctly?

I need a hint

The same count can represent different proportions. Missing data must remain visible in the conclusion.

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Take it with you

Compare four out of five and nine out of 15. Write one sentence about counts and another about proportions; add how three missing durations would affect your certainty.

At your own pace

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