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2.2.12 Variance and standard deviation

2.2.12 Variance and standard deviation

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Question 5

For a random sample of 50 employees, coded journey times x x\,x have ∑fx=815\sum fx=815∑fx=815 and ∑fx2=16475\sum fx^2=16475∑fx2=16475. The coding is x=t−202\displaystyle x=\frac{t-20}{2}x=2t−20​, where t t\,t is the actual time in minutes. Linear interpolation gives a coded median of 13.9.

a.

Estimate the sample standard deviation of xxx.

[3]
b.

Find the median and sample standard deviation of ttt.

[4]
Markscheme

2.2.12 Variance and standard deviation Questions

  1. A Level
  2. /Maths
  3. /2.2.12 Variance and standard deviation

8 exam-style questions on OCR (MEI) A Level Maths 2.2.12 Variance and standard deviation. Each one has a worked solution and a mark scheme showing where the marks go.

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