A-LevelMathematicsProbability and statistics9709/62 · May/June 2019 · Q45 Marks

It is known that 20% of male giant pandas in a certain area weigh more than 121 kg and 71.9% weigh more than 102 kg. Weights of male giant pandas in this area have a normal distribution.

(a)Find the mean and standard deviation of the weights of male giant pandas in this area.[5]

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

[B1] ± 0.842 seen but B0 if 1 ± 0.842 oe seen
[M1] One appropriate standardisation equation with a z-value, μ, σ and 121 or 102, condone continuity correction. Not 0.158, 0.42,...
[B1] ±0.58(0) seen but B0 if 1 ± 0.58 oe seen
[M1] Correct algebraic elimination of μ or σ from their two simultaneous equations to form an equation in one variable, condone 1 numerical slip
[A1] If M0A0 scored (i.e. no algebraic elimination seen), SC B1 can be awarded for both answers correct

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Topic: Probability and statistics, A-Level Mathematics (syllabus 9709). Structured question, 5 marks.
Source: A-Level Mathematics, May/June 2019 Paper 6 Variant 2, question 4.

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