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P4-P5 Probabilities sum to 1; sample size

Currently Secure · last touched 2026-10-05

Every change

WhenChangeEvidenceSession
2026-10-05Secure → SecureMixed round Q6, non-calc, unaided: dice rolled 12 times, 4 sixes, 'explain why the estimate may not be reliable' → 'the estemat is not reliable because the amont of roles is not big enoph'. Correct small-sample reason, 14 days after the last sample-size item (21 Sep).session 71
2026-10-02Secure → SecureMixed set Q1 unaided, non-calc: P(red) 0.35, P(blue) 0.4 → '1 - 0.35 = 0.65, 0.65 - 0.4 = 0.25, p = 0.25'; every working line before the answer.session 65
2026-09-28Secure → Secure28 Sep, non-calc: P(green) from P(red) 0.2, P(blue) 0.5 → '0.2 + 0.5 = 0.7, 1 - 0.7 = 0.3, so p(green) = 0.3' ✓ with every line written unasked.session 49
2026-09-21Secure → Secureaudit: bar met in session 34 — small-sample reasoning retested and closed: 7 heads in 10 flips judged not biased, unprompted, plus an unprompted expected-value comparison point.standalone
2026-09-21Secure → Secure21 Sep starter: 7 heads in 10 flips, 'biased' claim — gave small-sample reason unprompted plus '7 is only 2 more than the expected amount'. The small-sample reasoning loose end from 4 Sep is retested and closed.session 34
2026-09-11Developing → Secure11 Sep starter: council surveying 25 people at a bus stop — gave both the sample-size and the location-bias criticisms when only one was asked. Third session running with correct sampling reasoning.session 19
2026-09-10Developing → Developing9 Sep starter: fourth flavour 0.3, with 0.3+0.25+0.15 = 0.7 then 1 − 0.7 written out as separate steps rather than done mentally.session 17
2026-09-08Developing → Developing8 Sep starter: gave "40 puppies is too small a sample" as a criticism unprompted — the sample-size reasoning that was the weak half on 4 Sep.session 11
2026-09-07Developing → Developing7 Sep starter: spinner with red 0.2, blue 0.3 and two equally likely colours → P(green) = 0.25. Two-step, correct, independent.session 7
2026-09-07Gap → DevelopingTaught 4 Sep. 1 − P(A) correct on decimals and fractions incl. 5/12 via common denominator unprompted; 0.35 × 60 = 21. Exit ticket 4/5 — Q4 correct only after a prompt, Q5 answered the wrong question. Taught and tested same session.session 6

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