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A-LevelMathematicsProbability and statistics9709/63 · May/June 2020 · Q13 Marks

A random sample of 100 values of a variable X is taken. These values are summarised below. n = 100 Σχ = 1556 Σχ² = 29004 Calculate unbiased estimates of the population mean and variance of X.

  1. Calculate unbiased estimates of the population mean and variance of X.[3]

Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

  1. [B1] Est μ = 15.56
  2. [M1] Est σ² = (100/99)(29004/100 – 15.56²) or (1/99)(29004 – 1556²/100)
  3. [A1] 48.4105 = 48.4 (3 sf)

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About this question

Topic
Probability and statistics, A-Level Mathematics (syllabus 9709). Structured question, 3 marks.
Source
A-Level Mathematics, May/June 2020 Paper 6 Variant 3, question 1.

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